Remove TCMALLOC_PERCPU_STRINGIFY
Remove TCMALLOC_PERCPU_STRINGIFY

The TCMALLOC_PERCPU_STRINGIFY preprocessor macro is broken - it was not updated
to reference TCMALLOC_PERCPU_XSTRINGIFY when it was renamed from
PERCPU_XSTRINGIFY. Fortunately it's also unused. Remove the dead code.

PiperOrigin-RevId: 380203539
Change-Id: I71f8e086eabfe36dab59cdb455ed72f426b8a9d9

google/tcmalloc,google/tcmalloc,google/tcmalloc