Update tests to use latest neovim 0.7 (#4180)

* Update tests to use latest neovim 0.7

* Update CI to use neovim 0.7

* Fix conflict

.github/workflows/main.yml

@@ -29,7 +29,7 @@ jobs:
           - '--vim-80-only'
           - '--vim-82-only'
           - '--neovim-02-only'
-          - '--neovim-06-only'
+          - '--neovim-07-only'
           - '--linters-only'
     steps:
       - uses: actions/checkout@v2