workflow: Change Ubuntu Xenial builder to Bionic

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
 
       matrix:
         profile:
-        - ubuntu-xenial-standard-unity-makefile
+        - ubuntu-bionic-standard-unity-makefile
         - ubuntu-bionic-coverage-ninja
         - macos-eigen-coverage-unity-xcode
         - macos-nometa-standard-makefile
@@ -19,8 +19,8 @@ jobs:
         - windows-nopython-nometa-standard-msvc
 
         include:
-        - profile: ubuntu-xenial-standard-unity-makefile
-          os: ubuntu-16.04
+        - profile: ubuntu-bionic-standard-unity-makefile
+          os: ubuntu-18.04
           config: Standard
           unity: YES
           generator: Unix Makefiles