[clang] [docs] Fix the use of word "dependent" and other typos in the C++ Modules Doc (PR #136719)

[Chuanqi Xu via cfe-commits]

https://github.com/ChuanqiXu9 approved this pull request.

I am not a native speaker. So LGTM generally.

https://github.com/llvm/llvm-project/pull/136719