[clang-format] format applied to // clang-format off annotation

[yshui]

Example: https://github.com/yshui/picom/blob/d91e260f2738c765f72e9e990bfecf1baa76a70f/src/options.c#L399

clang-format configuration: https://github.com/yshui/picom/blob/next/.clang-format

When formatted, clang-format will try to add an extra level of indentation to // clang-format off, which, even not considering the fact that this line is telling clang-format to not touch it, is still wrong.