Jump to 18.04 as it offers Tidy extension by default too

.github/workflows/coding-standards.yml

@@ -11,7 +11,7 @@ on:
 jobs:
   coding-standards:
     name: "CS Fixer & PHPStan"
-    runs-on: "ubuntu-16.04"
+    runs-on: "ubuntu-18.04"
 
     steps:
       - name: "Checkout"

.github/workflows/continuous-integration.yml

@@ -15,7 +15,7 @@ env:
 jobs:
   phpunit:
     name: "PHP ${{ matrix.php }} using ${{ matrix.database }}"
-    runs-on: "ubuntu-16.04"
+    runs-on: "ubuntu-18.04"
     services:
       rabbitmq:
         image: rabbitmq:3-alpine

.github/workflows/translations.yml

@@ -11,7 +11,7 @@ on:
 jobs:
   translations:
     name: "Translations"
-    runs-on: "ubuntu-16.04"
+    runs-on: "ubuntu-18.04"
 
     strategy:
       matrix: