os: remove redundant GOOS checks in chown tests

The build tags already prevent the tests from being run on windows or
plan9, so there is no need to check GOOS again.

Change-Id: I74d3c3b7756d9c50f6e5fd4c3e8b0db618fdebbb
Reviewed-on: https://go-review.googlesource.com/81295
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/os/os_unix_test.go

@@ -36,11 +36,6 @@ func checkUidGid(t *testing.T, path string, uid, gid int) {
 }
 
 func TestChown(t *testing.T) {
-	// Chown is not supported under windows or Plan 9.
-	// Plan9 provides a native ChownPlan9 version instead.
-	if runtime.GOOS == "windows" || runtime.GOOS == "plan9" {
-		t.Skipf("%s does not support syscall.Chown", runtime.GOOS)
-	}
 	// Use TempDir() to make sure we're on a local file system,
 	// so that the group ids returned by Getgroups will be allowed
 	// on the file. On NFS, the Getgroups groups are
@@ -84,10 +79,6 @@ func TestChown(t *testing.T) {
 }
 
 func TestFileChown(t *testing.T) {
-	// Fchown is not supported under windows or Plan 9.
-	if runtime.GOOS == "windows" || runtime.GOOS == "plan9" {
-		t.Skipf("%s does not support syscall.Fchown", runtime.GOOS)
-	}
 	// Use TempDir() to make sure we're on a local file system,
 	// so that the group ids returned by Getgroups will be allowed
 	// on the file. On NFS, the Getgroups groups are
@@ -131,10 +122,6 @@ func TestFileChown(t *testing.T) {
 }
 
 func TestLchown(t *testing.T) {
-	// Lchown is not supported under windows or Plan 9.
-	if runtime.GOOS == "windows" || runtime.GOOS == "plan9" {
-		t.Skipf("%s does not support syscall.Lchown", runtime.GOOS)
-	}
 	// Use TempDir() to make sure we're on a local file system,
 	// so that the group ids returned by Getgroups will be allowed
 	// on the file. On NFS, the Getgroups groups are