[cli] remove --execute

This was introduced and deprecated at the same time in #6862, which seems rather pointless.

src/compiler/main.ml

@@ -535,7 +535,7 @@ try
 		("Target",["--hl"],["-hl"],Arg.String (fun file ->
 			Initialize.set_platform com Hl file;
 		),"<file>","compile HL code as target file");
-		("Target",[],["-x";"--execute"], Arg.String (fun cl ->
+		("Target",[],["-x"], Arg.String (fun cl ->
 			let cpath = Path.parse_type_path cl in
 			(match com.main_class with
 				| Some c -> if cpath <> c then raise (Arg.Bad "Multiple --main classes specified")