[libcxxabi][test][NFC] Turn off clang-format for demangler test-case array (#73503)

Adding test-cases to the `cases` array causes `git clang-format` to
split the strings of many of the existing test-cases, making them harder
to read/work with in most cases.

This patch disables `clang-format` for the `cases` array so it doesn't
catch anyone off-guard in the future.

Author: Michael137

libcxxabi/test/test_demangle.pass.cpp

@@ -32,6 +32,7 @@
 // Is long double fp128?
 #define LDBL_FP128 (__LDBL_MANT_DIG__ == 113)
 
+// clang-format off
 const char* cases[][2] =
 {
     {"_Z1A", "A"},
@@ -30175,6 +30176,7 @@ const char* cases[][2] =
     {"_Z2f5IPiEvu16__remove_pointerIT_E", "void f5<int*>(__remove_pointer(int*))"},
     {"_Z2f5IiEvu14__remove_cvrefIT_E", "void f5<int>(__remove_cvref(int))"},
 };
+// clang-format on
 
 const unsigned N = sizeof(cases) / sizeof(cases[0]);