Use official Github Action

It is more concise.

.github/workflows/static-analysis.yml

@@ -55,24 +55,8 @@ jobs:
           - "7.4"
 
     steps:
-      - name: "Checkout code"
-        uses: "actions/checkout@v2"
-
-      - name: "Install PHP"
-        uses: "shivammathur/setup-php@v2"
-        with:
-          coverage: "none"
-          php-version: "${{ matrix.php-version }}"
-
-      - name: "Cache dependencies installed with composer"
-        uses: "actions/cache@v2"
-        with:
-          path: "~/.composer/cache"
-          key: "php-${{ matrix.php-version }}-composer-locked-${{ hashFiles('composer.lock') }}"
-          restore-keys: "php-${{ matrix.php-version }}-composer-locked-"
-
-      - name: "Install dependencies with composer"
-        run: "composer install --no-interaction --no-progress --no-suggest"
+      - name: Checkout code
+        uses: actions/checkout@v2
 
-      - name: "Run a static analysis with vimeo/psalm"
-        run: "vendor/bin/psalm --show-info=false --stats --output-format=github --threads=4"
+      - name: Psalm
+        uses: docker://vimeo/psalm-github-actions