ci: Roll back prettier version to work with prettier-php (#225)

.github/workflows/prettier.yml

@@ -6,6 +6,7 @@ on:
       - main
   pull_request:
     paths:
+      - ".github/workflows/prettier.yml"
       - "**.php"
       - "**.md"
       - "**.js"
@@ -27,7 +28,7 @@ jobs:
         uses: actions/checkout@v3
 
       - name: Install prettier and plugin-php
-        run: npm install --global prettier @prettier/plugin-php
+        run: npm install --global prettier@"^1.15.0 || ^2.0.0" @prettier/plugin-php
 
       - name: Check formatting with Prettier
         continue-on-error: true