Remove mention of neovim as the checkhealth syntax is deprecated there (#1525)

Co-authored-by: Prabir Shrestha <[email protected]>

Author: dundargoc

Diff for: README.md

@@ -183,7 +183,7 @@ let g:lsp_log_file = expand('~/vim-lsp.log')
 let g:asyncomplete_log_file = expand('~/asyncomplete.log')
 ```
 
-You can get detailed status on your servers using `:CheckHealth` -- built into neovim or in a plugin on vim:
+You can get detailed status on your servers using `:CheckHealth` with a plugin on vim:
 
 ```vim
 if !has('nvim') | Plug 'rhysd/vim-healthcheck' | endif

Diff for: doc/vim-lsp.txt

@@ -289,7 +289,7 @@ HEALTH CHECK						*vim-lsp-healthcheck*
 vim-lsp supports the |:CheckHealth| command which can be useful when debugging
 lsp configuration issues.
 
-This command is included in neovim and implemented in vim with the
+This command is implemented in vim with the
 [vim-healthcheck](https://github.com/rhysd/vim-healthcheck) plugin. 
 
 WIKI                                               *vim-lsp-configure-wiki*