c++: adjust comment to align with new default c++20

After r16-5628-g004438857554f4, the default C++ standard is now c++20. Update
the comment here accordingly.

gcc/c-family/ChangeLog:

	* c-common.h (enum cxx_dialect): c++17 to c++20.

diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index 6a92bd6ef762819f88a554b0719458626efe8c10..4b63f5d13095707f399b36e944c203bee2a0609a 100644 (file)
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -748,7 +748,7 @@ enum cxx_dialect {
   cxx26
 };
 
-/* The C++ dialect being used.  C++17 is the default.  */
+/* The C++ dialect being used.  C++20 is the default.  */
 extern enum cxx_dialect cxx_dialect;
 
 /* Maximum template instantiation depth.  This limit is rather