Fix yamllint errors

.github/workflows/ci.yml

@@ -1,6 +1,7 @@
+---
 name: CI
 
-on:
+on:  # yamllint disable-line rule:truthy
   pull_request:
   push:
 
@@ -13,7 +14,10 @@ jobs:
         php: [7.3, 7.4]
         dependency-version: [prefer-lowest, prefer-stable]
 
-    name: P${{ matrix.php }} - ${{ matrix.dependency-version }} - ${{ matrix.os }}
+    name: >
+      P${{ matrix.php }}-
+      ${{ matrix.dependency-version }}-
+      ${{ matrix.os }}
 
     steps:
       - name: Checkout code
@@ -23,7 +27,10 @@ jobs:
         uses: actions/cache@v1
         with:
           path: ~/.composer/cache/files
-          key: dependencies-php-${{ matrix.php }}-composer-${{ hashFiles('composer.json') }}
+          key: >
+            dependencies-
+            php-${{ matrix.php }}-
+            composer-${{ hashFiles('composer.json') }}
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v1
@@ -34,7 +41,8 @@ jobs:
       - name: Install dependencies
         run: |
           composer install
-          composer update --${{ matrix.dependency-version }} --prefer-dist --no-interaction --no-suggest
+          composer update --${{ matrix.dependency-version }} \
+            --prefer-dist --no-interaction --no-suggest
 
       - name: Execute tests
         run: make test