use gutentags only in php

this avoids unwantes `tags` files everywhere

init.vim

@@ -31,7 +31,7 @@ Plug 'lambdalisue/suda.vim' " As w!! did not work anymore in nvim
 Plug 'https://github.com/alok/notational-fzf-vim' " note taking
 Plug 'prettier/vim-prettier', { 'do': 'npm install' } " prettier integration
 Plug 'honza/vim-snippets' " Collection of Snippets, used by coc-snippet
-Plug 'ludovicchabant/vim-gutentags' " Keep tags in sync
+Plug 'ludovicchabant/vim-gutentags', { 'for': 'php' } " Keep tags in sync
 
 " {{{ CocPlugins
 Plug 'neoclide/coc-json', { 'do': 'yarn install --frozen-lockfile' }