grename: fail to echo error message at validate arguments

[tranmt09]

The error occurs when it tries to display the error message.

❯ grename test-rename
status: Unknown option '-u'

~/.config/fish/functions/grename.fish (line 1): 
in command substitution
        called on line 4 of file ~/.config/fish/functions/grename.fish
in function 'grename' with arguments 'test-rename'

(Type 'help status' for related documentation)

Suggestion to change the argument of status command to current-command

 echo "Usage: "(status current-command)" old_branch new_branch"