[clang] [clang-format][NFC] Eliminate the IsCpp parameter in all functions (PR #84599)

[Benjamin Kramer via cfe-commits]

d0k wrote:

It calls `clang::format::cleanupAroundReplacements` from multiple threads. Now there's a race condition on IsCpp.

If this was supposed to be a cleanup please revert it.

https://github.com/llvm/llvm-project/pull/84599