[TLI] fix a function's (commented) signature; NFC

__strlen_chk returns a `size_t`, not a `char *`.

llvm/include/llvm/Analysis/TargetLibraryInfo.def

@@ -434,7 +434,7 @@ TLI_DEFINE_STRING_INTERNAL("__strlcat_chk")
 ///                      size_t dstsize);
 TLI_DEFINE_ENUM_INTERNAL(strlcpy_chk)
 TLI_DEFINE_STRING_INTERNAL("__strlcpy_chk")
-/// char *__strlen_chk(const char *s1, size_t s1size);
+/// size_t __strlen_chk(const char *s1, size_t s1size);
 TLI_DEFINE_ENUM_INTERNAL(strlen_chk)
 TLI_DEFINE_STRING_INTERNAL("__strlen_chk")
 /// char *strncat_chk(char *s1, const char *s2, size_t n, size_t s1size);