[libc] Fix long double is double double const

Turns out for double double LDBL_MANT_DIG == 106. This patch fixes the
constant. Should fix the ppc buildbot.

Previously:
llvm#113235
llvm#113237
llvm#91651

Author: michaelrj-google

libc/src/__support/macros/properties/types.h

@@ -27,7 +27,7 @@
 #define LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80
 #elif (LDBL_MANT_DIG == 113)
 #define LIBC_TYPES_LONG_DOUBLE_IS_FLOAT128
-#elif (LDBL_MANT_DIG == 103)
+#elif (LDBL_MANT_DIG == 106)
 #define LIBC_TYPES_LONG_DOUBLE_IS_DOUBLE_DOUBLE
 #endif