Upgrade gh-actions to Ubuntu 22.04

The newer GCC does a better job of reducing code size.

.github/workflows/ci.yml

@@ -5,7 +5,7 @@ on: [push, pull_request]
 jobs:
 
   build-ubuntu:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
 
     - uses: actions/checkout@v3

.github/workflows/release.yml

@@ -8,7 +8,7 @@ name: Release
 jobs:
 
   build-ubuntu:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
 
     - uses: actions/checkout@v3
@@ -39,7 +39,7 @@ jobs:
 
   finalise:
     needs: build-ubuntu
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
 
     - uses: actions/checkout@v3