[clang] [clang] Rename -Wdeprecated-switch-case to -Wdeprecated-declarations-switch-case (PR #141779)

[Nico Weber via cfe-commits]

nico wrote:

The release notes here https://github.com/llvm/llvm-project/pull/138562/files#diff-ec770381d76c859f5f572db789175fe44410a72608f58ad5dbb14335ba56eb97R525 need updating too, right?

https://github.com/llvm/llvm-project/pull/141779