apidiff: skip TestChanges

Temporarily skip running TestChanges. A recent compiler change
causes apidiff to panic. Skipping until we have time to analyze properly.

Change-Id: I4fdd0fdc6c2de5a8afd5f401537018903bf69fe7
Reviewed-on: https://go-review.googlesource.com/c/exp/+/442357
Run-TryBot: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

apidiff/apidiff_test.go

@@ -17,6 +17,7 @@ import (
 )
 
 func TestChanges(t *testing.T) {
+	t.Skip("broken by go1.20-pre3 compiler: see https://go.dev/issue/56162")
 	dir, err := os.MkdirTemp("", "apidiff_test")
 	if err != nil {
 		t.Fatal(err)