client: fix handling of "-m" command-line flag

CHANGELOG.md

@@ -88,6 +88,7 @@
 * Key mappings for key combinations with `shift`+`tab`
   (https://codeberg.org/dnkl/foot/issues/210).
 * Key mappings for key combinations with `alt`+`return`.
+* `footclient` `-m` (`--maximized`) flag being ignored.
 
 
 ### Security

client.c

@@ -100,7 +100,7 @@ main(int argc, char *const *argv)
             login_shell = true;
             break;
 
-        case ',':
+        case 'm':
             maximized = true;
             fullscreen = false;
             break;