ci: remove ubuntu-20.04 (EOL)

Signed-off-by: Sebastiaan van Stijn <[email protected]>

Author: thaJeztah

Diff for: .github/workflows/test.yml

@@ -5,7 +5,7 @@ jobs:
     strategy:
       matrix:
         go-version: [1.18.x, 1.23.x, 1.24.x]
-        platform: [ubuntu-20.04, ubuntu-22.04, ubuntu-24.04, windows-latest, macos-13, macos-14, macos-15]
+        platform: [ubuntu-22.04, ubuntu-24.04, windows-latest, macos-13, macos-14, macos-15]
     runs-on: ${{ matrix.platform }}
     defaults:
       run: