Rename cl to size_class in percpu_tcmalloc_test.cc.
Rename cl to size_class in percpu_tcmalloc_test.cc.

Note: generated with regexp replace: "(\b|_)cl(\b|_)" to "\1size_class\2".
PiperOrigin-RevId: 420341159
Change-Id: Ife7812b9d465d7ac178c386afdad73200ec246c7

google/tcmalloc,google/tcmalloc,google/tcmalloc