go/parser: fix reference in ParseExprFrom docs

The ParseExprFrom docs refer to Parse. It meant ParseFile.

Fixes #18398

Change-Id: I06fb3b5178c6319e86199823fe4769a8eb9dc49c
Reviewed-on: https://go-review.googlesource.com/34671Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/go/parser/interface.go

@@ -173,7 +173,7 @@ func ParseDir(fset *token.FileSet, path string, filter func(os.FileInfo) bool, m
 }
 
 // ParseExprFrom is a convenience function for parsing an expression.
-// The arguments have the same meaning as for Parse, but the source must
+// The arguments have the same meaning as for ParseFile, but the source must
 // be a valid Go (type or value) expression. Specifically, fset must not
 // be nil.
 //