go/types: remove unused alias-related testdata files

They interfere with gofmt -w across this directory.

Follow-up on https://go-review.googlesource.com/32819.

For #16339 (comment).

Change-Id: I4298b6117d89517d4fe6addce3942d950d821817
Reviewed-on: https://go-review.googlesource.com/33019Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/go/types/testdata/alias.go

-// Copyright 2016 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Used by TestAliases (api_test.go).
-
-package alias
-
-import (
-	"go/build"
-	"math"
-)
-
-const Pi1 => math.Pi
-const Pi2 => math.Pi // cause the same object to be exported multiple times (issue 17726)
-
-var Default => build.Default
-
-type Context => build.Context
-
-func Sin => math.Sin

src/go/types/testdata/aliasdecl.src

-// Copyright 2016 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package aliasdecl
-
-import (
-	"flag"
-	"fmt" // use at most once (to test "imported but not used" error)
-	"go/build"
-	. "go/build"
-	"io"
-	"math"
-	"unsafe"
-)
-
-// helper
-var before struct {
-	f int
-}
-
-// aliases must refer to package-qualified identifiers
-type _ => _ /* ERROR "_ is not a package-qualified identifier" */
-type t1 => _ /* ERROR "_ is not a package-qualified identifier" */
-
-const _ => iota /* ERROR "iota is not a package-qualified identifier" */
-type _ => int   /* ERROR "int is not a package-qualified identifier" */
-
-const c => iota /* ERROR "iota is not a package-qualified identifier" */
-type t2 => int   /* ERROR "int is not a package-qualified identifier" */
-
-// dot-imported identifiers are not qualified identifiers
-// TODO(gri) fix error printing - should not print a qualified identifier...
-var _ => Default /* ERROR "Default is not a package-qualified identifier" */
-
-// qualified identifiers must start with a package
-var _ => before /* ERROR "before.f is not a package-qualified identifier" */ .f
-func _ => before /* ERROR "before.f is not a package-qualified identifier" */ .f
-var _ => after /* ERROR "after.m is not a package-qualified identifier" */ .m
-func _ => after /* ERROR "after.m is not a package-qualified identifier" */ .m
-
-var v1 => before /* ERROR "before.f is not a package-qualified identifier" */ .f
-func f1 => before /* ERROR "before.f is not a package-qualified identifier" */ .f
-var v2 => after /* ERROR "after.m is not a package-qualified identifier" */ .m
-func f2 => after /* ERROR "after.m is not a package-qualified identifier" */ .m
-
-// TODO(gri) fix error printing - should print correct qualified identifier...
-var _ => Default /* ERROR "Default.ARCH is not a package-qualified identifier" */ .ARCH
-var _ Context // use dot-imported package go/build
-
-// aliases may not refer to package unsafe
-type ptr => unsafe /* ERROR "refers to package unsafe" */ .Pointer
-func size => unsafe /* ERROR "refers to package unsafe" */ .Sizeof
-
-// aliases must refer to entities of the same kind
-const _ => math.Pi
-const pi => math.Pi
-const pi1 => math /* ERROR "math.Sin.* is not a constant" */ .Sin
-
-type _ => io.Writer
-type writer => io.Writer
-type writer1 => math /* ERROR "math.Sin.* is not a type" */ .Sin
-
-var _ => build.Default
-var def => build.Default
-var def1 => build /* ERROR "build.Import.* is not a variable" */ .Import
-
-func _ => math.Sin
-func sin => math.Sin
-func sin1 => math /* ERROR "math.Pi.* is not a function" */ .Pi
-
-// using an incorrectly declared alias should not lead to more errors
-const _ = pi1
-type _ writer1
-var _ def1 = 0
-var _ = sin1
-
-// aliases may not be called init
-func init /* ERROR "cannot declare init" */ => flag.Parse
-func _ => flag.Parse // use package flag
-
-// alias reference to a package marks package as used
-func _ => fmt.Println
-
-// re-exported aliases
-const Pi => math.Pi
-
-type Writer => io.Writer
-
-var Def => build.Default
-
-func Sin => math.Sin
-
-// const aliases may appear in "iota" context
-// (this verifies a type-checker internal assertion)
-const (
-	_ = iota
-	pi2 => math.Pi
-)
-
-// type aliases denote identical types
-type myPackage => build.Package
-
-var pkg myPackage
-var _ build.Package = pkg   // valid assignment
-var _ *build.Package = &pkg // valid assignment
-
-// helper
-type after struct{}
-
-func (after) m() {}