change common.hpp to avoid warnings

Changed the code to disable use of C++26 features. The way to restore that is probably adding/removing warning suppression in `suppress_push.hpp` and `suppress_pop.hpp` but I think this PR isn't the place to do that.

Author: dietmarkuehl

include/beman/execution26/detail/common.hpp

@@ -6,7 +6,7 @@
 
 // ----------------------------------------------------------------------------
 
-#if defined(__cpp_deleted_function)
+#if defined(disabled__cpp_deleted_function)
 #define BEMAN_EXECUTION26_DELETE(msg) delete (msg)
 #else
 #define BEMAN_EXECUTION26_DELETE(msg) delete