GHA: Don't build on older Linux'ee

Try 5.5.0-bionic

Author: helje5

.github/workflows/swift.yml

@@ -13,8 +13,7 @@ jobs:
       fail-fast: false
       matrix:
         image:
-          - swift:5.0.3-xenial
-          - swift:5.3.2-bionic
+          - swift:5.5.0-bionic
           - swift:5.10.1-noble
     container: ${{ matrix.image }}
     steps: