plugins: remove uneccessary config for COC

* Removes key mapping for the coc-completion which does not use the
  built-in vim completion mechanism anymore.

Co-Authored-by: iGor milhit <igor@milhit.ch>

init.vim

@@ -190,29 +190,6 @@ else
   set signcolumn=yes
 endif
 
-" Use tab for trigger completion with characters ahead and navigate
-inoremap <silent><expr> <TAB>
-      \ pumvisible() ? "\<C-n>" :
-      \ <SID>check_back_space() ? "\<TAB>" :
-      \ coc#refresh()
-inoremap <expr><S-TAB> pumvisible() ? "\<C-p>" : "\<C-h>"
-
-function! s:check_back_space() abort
-  let col = col('.') - 1
-  return !col || getline('.')[col - 1]  =~# '\s'
-endfunction
-" Use <c-space> to trigger completion.
-if has('nvim')
-  inoremap <silent><expr> <c-space> coc#refresh()
-else
-  inoremap <silent><expr> <c-@> coc#refresh()
-endif
-
-" Make <CR> auto-select the first completion item and notify coc.nvim to
-" format on enter, <cr> could be remapped by other vim plugin
-inoremap <silent><expr> <cr> pumvisible() ? coc#_select_confirm()
-                              \: "\<C-g>u\<CR>\<c-r>=coc#on_enter()\<CR>"
-
 " Use `[g` and `]g` to navigate diagnostics
 " Use `:CocDiagnostics` to get all diagnostics of current buffer in location list.
 nmap <silent> [g <Plug>(coc-diagnostic-prev)