ci: use arm macOS version of nightly neovim (#83)

Author: cpea2506

.github/workflows/test.yaml

@@ -18,12 +18,12 @@ jobs:
           - os: ubuntu-latest
             neovim: nightly
             url: https://github.com/neovim/neovim/releases/download/nightly/nvim-linux64.tar.gz
-          - os: macos-latest
+          - os: macos-14
             neovim: stable
             url: https://github.com/neovim/neovim/releases/download/stable/nvim-macos.tar.gz
-          - os: macos-latest
+          - os: macos-14
             neovim: nightly
-            url: https://github.com/neovim/neovim/releases/download/nightly/nvim-macos.tar.gz
+            url: https://github.com/neovim/neovim/releases/download/nightly/nvim-macos-arm64.tar.gz
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v2