test suite: Use 'say' to say something instead of 'test_expect_success'

Some tests report that some tests will be skipped.  They used
'test_expect_success' with a trivially successful test.  Nowadays we have
the helper function 'say' for this purpose.

In on case, 'say_color skip' is replaced by 'say' because the former is
not intended as a public API.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>

t/t9500-gitweb-standalone-no-errors.sh

@@ -74,7 +74,7 @@ safe_chmod () {
 . ./test-lib.sh
 
 perl -MEncode -e 'decode_utf8("", Encode::FB_CROAK)' >/dev/null 2>&1 || {
-    test_expect_success 'skipping gitweb tests, perl version is too old' :
+    say 'skipping gitweb tests, perl version is too old'
     test_done
     exit
 }