[clang] [llvm] [ADT] Deprecate variadic `StringSwitch::CasesLower`. NFC. (PR #166016)

[Jan Patrick Lehr via cfe-commits]

jplehr wrote:

We see the same failures in our libc on GPU bot: https://lab.llvm.org/staging/#/builders/43/builds/5333

https://github.com/llvm/llvm-project/pull/166016