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

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 <redacted>