Use PHP 7.4 for static analysis

Author: sebastianbergmann

.github/workflows/ci.yml

@@ -17,7 +17,7 @@ jobs:
         uses: "actions/checkout@v2"
 
       - name: "Run friendsofphp/php-cs-fixer"
-        run: "php7.3 ./tools/php-cs-fixer fix --diff-format=udiff --dry-run --show-progress=dots --using-cache=no --verbose"
+        run: "php7.4 ./tools/php-cs-fixer fix --diff-format=udiff --dry-run --show-progress=dots --using-cache=no --verbose"
 
   type-checker:
     name: "Type Checker"
@@ -31,15 +31,15 @@ jobs:
       - name: "Install PHP with extensions"
         uses: "shivammathur/setup-php@v2"
         with:
-          php-version: "7.3"
+          php-version: "7.4"
           coverage: "pcov"
 
       - name: "Cache dependencies installed with composer"
         uses: "actions/cache@v2"
         with:
           path: "~/.composer/cache"
-          key: "php7.3-composer-${{ hashFiles('**/composer.json') }}"
-          restore-keys: "php7.3-composer-"
+          key: "php7.4-composer-${{ hashFiles('**/composer.json') }}"
+          restore-keys: "php7.4-composer-"
 
       - name: "Set COMPOSER_ROOT_VERSION environment variable"
         uses: "docker://ergebnis/composer-root-version-action:0.1.3"