Minor rebranding

There's nothing experimental about this project anymore.  It's stable.

Maybe we should add a photo of Hitler or something.

degesch.c

@@ -1,5 +1,5 @@
 /*
- * degesch.c: the experimental IRC client
+ * degesch.c: a terminal-based IRC client
  *
  * Copyright (c) 2015 - 2020, Přemysl Eric Janouch <p@janouch.name>
  *
@@ -14064,7 +14064,7 @@ main (int argc, char *argv[])
 	};
 
 	struct opt_handler oh =
-		opt_handler_make (argc, argv, opts, NULL, "Experimental IRC client.");
+		opt_handler_make (argc, argv, opts, NULL, "Terminal-based IRC client.");
 	bool format_mode = false;
 
 	int c;