Remove __RENAME_LDBL.

Discussion of this during my recent minor cleanup convinced me that we
should just remove __RENAME_LDBL. There's no obvious benefit to being
able to build something for 32-bit if you can't build the same code for
64-bit, given that most new hardware (and entire verticals such as Auto)
are 64-bit-only, and the Play Store requires any app with 32-bit code to
also ship 64-bit code.

Test: treehugger
Change-Id: I1c5503b968ca66925d7bd125bd3630c41ec1bfd0
diff --git a/libc/include/stdlib.h b/libc/include/stdlib.h
index 2bcb870..ee4b12a 100644
--- a/libc/include/stdlib.h
+++ b/libc/include/stdlib.h
@@ -78,7 +78,7 @@
 void* _Nullable aligned_alloc(size_t __alignment, size_t __size) __INTRODUCED_IN(28);
 
 double strtod(const char* _Nonnull __s, char* _Nullable * _Nullable __end_ptr);
-long double strtold(const char* _Nonnull __s, char* _Nullable * _Nullable __end_ptr) __RENAME_LDBL(strtod, 3, 21);
+long double strtold(const char* _Nonnull __s, char* _Nullable * _Nullable __end_ptr) __INTRODUCED_IN(21);
 
 unsigned long strtoul_l(const char* _Nonnull __s, char* _Nullable * _Nullable __end_ptr, int __base, locale_t _Nonnull __l) __INTRODUCED_IN(26);