Configure cmake-language-server and coc-cmake

Utilises the following Python package:

```console
$ pip3 install --user cmake-language-server
```

vimrc

@@ -40,8 +40,6 @@ Pack 'neoclide/coc.nvim', {'branch': 'release'}
 " ultisnips - snippet engine
 Pack 'SirVer/ultisnips'
 Pack 'honza/vim-snippets'
-" vim-cmake-completion - completion & help
-Pack 'kbenzie/vim-cmake-completion', {'type': 'opt'}
 " vimomni - Completion for vimscript
 Pack 'vim-scripts/vimomni', {'type': 'opt'}