Change to correct argument to report accurate error message (#853)

* Change to correct argument to report accurate error message

* Update pkg/omf/functions/cli/omf.cli.theme.fish
Co-authored-by: Pablo Aguiar <scorphus@gmail.com>
Co-authored-by: Pablo Aguiar <scorphus@gmail.com>

pkg/omf/functions/cli/omf.cli.theme.fish

@@ -21,7 +21,7 @@ function omf.cli.theme -a name
     end
   case '*'
     echo (omf::err)"Invalid number of arguments"(omf::off) >&2
-    echo "Usage: $_ "(omf::em)"$argv[1]"(omf::off)" [<theme name>]" >&2
+    echo "Usage: $_ "(omf::em)"t"(omf::off)"heme [<theme name>]" >&2
     return $OMF_INVALID_ARG
   end
 end