Use merged setup-emacs action (#703)

Author: jcs090218

.github/workflows/test.yml

@@ -23,13 +23,7 @@ jobs:
           - snapshot
 
     steps:
-      - uses: purcell/setup-emacs@master
-        if: matrix.os == 'ubuntu-latest' || matrix.os == 'macos-latest'
-        with:
-          version: ${{ matrix.emacs-version }}
-
-      - uses: jcs090218/setup-emacs-windows@master
-        if: matrix.os == 'windows-latest'
+      - uses: jcs090218/setup-emacs@master
         with:
           version: ${{ matrix.emacs-version }}