Incorrect method used to remove plugin/ if not needed.

[lienzhuzhu]

I just used this template and found that there is an incorrect line in the python script. If the user selects 'n' to the question asking if the plugin folder is needed or not, then line 45 of the script fails, as os.remove() only removes files, not directories. I will put in a pull request with the corrected line.

> python rename.py bug
Renamed files under plugin folder successed
Renamed files under lua folder successed
Ci yaml has been updated
Renamed files under doc folder successed
Do you need plugin folder in your plugin (y|n): n
Traceback (most recent call last):
  File "<my home directory>/nvim-projects/bug/rename.py", line 45, in <module>
    os.remove(os.path.join(os.getcwd(), 'plugin'))
PermissionError: [Errno 1] Operation not permitted: '<my home directory>/nvim-projects/bug/plugin'