[libcxx] Remove ifdefs in the message to static_assert. NFC.

Differential Revision: https://reviews.llvm.org/D93283

GitOrigin-RevId: 08a00c6f43c187f8fb3b08dd98e269fb1fcff836
diff --git a/include/filesystem b/include/filesystem
index 1a44d9f..764ec65 100644
--- a/include/filesystem
+++ b/include/filesystem
@@ -1236,11 +1236,7 @@
 #endif
       is_same<typename __is_pathable<_Source>::__char_type, char>::value,
       "u8path(Source const&) requires Source have a character type of type "
-      "'char'"
-#ifndef _LIBCPP_NO_HAS_CHAR8_T
-      " or 'char8_t'"
-#endif
-      );
+      "'char' or 'char8_t'");
   return path(__s);
 }
 
@@ -1254,10 +1250,7 @@
 #endif
       is_same<typename __is_pathable<_InputIt>::__char_type, char>::value,
       "u8path(Iter, Iter) requires Iter have a value_type of type 'char'"
-#ifndef _LIBCPP_NO_HAS_CHAR8_T
-      " or 'char8_t'"
-#endif
-      );
+      " or 'char8_t'");
   return path(__f, __l);
 }