Use Ubuntu-20.04 in github actions

.github/workflows/build-ci.yml

@@ -95,7 +95,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-16.04]
+        os: [ubuntu-20.04]
 
     steps:
     # Checkout the repository as $GITHUB_WORKSPACE
@@ -125,7 +125,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-16.04]
+        os: [ubuntu-20.04]
 
     # Steps represent a sequence of tasks that will be executed as part of the job
     steps:

.github/workflows/clang-format.yml

@@ -16,7 +16,7 @@ jobs:
     timeout-minutes: 5
 
     # Ubuntu 18.04 at the time of writing includes clang-format-9 as default
-    runs-on: [ubuntu-18.04]
+    runs-on: [ubuntu-20.04]
 
     # We want to check all changed files between the pull-request base and the head of the pull request
     env: