googletest

Restore GTEST_ATTRIBUTE_PRINTF_ on ColoredPrintf

This fixes build issues with GoogleTest when built with
-Wformat-nonliteral and unblocks updating GoogleTest in BoringSSL.

It was added in 53c478d639b8eebd2942e88266610ebc79c541f6, which caught
some bugs. Then it was moved to the header and accidentally dropped in
482ac6ee63429af2aa9c44f4e6427873fb68fb1f.