fmt: fix documention for %#v on uints

It's the same as %#x not %x.

Just a documentation change; tests already cover it.

Fixes #17322

Change-Id: Ia9db229f781f9042ac5c0bb824e3d7a26fb74ec5
Reviewed-on: https://go-review.googlesource.com/31254Reviewed-by: Russ Cox <rsc@golang.org>

src/fmt/doc.go

@@ -51,7 +51,7 @@
 	The default format for %v is:
 		bool:                    %t
 		int, int8 etc.:          %d
-		uint, uint8 etc.:        %d, %x if printed with %#v
+		uint, uint8 etc.:        %d, %#x if printed with %#v
 		float32, complex64, etc: %g
 		string:                  %s
 		chan:                    %p