Update ci.yml

Author: adam-fowler

Diff for: .github/workflows/ci.yml

@@ -8,27 +8,17 @@ on:
     - '**.swift'
     - '**.yml'
   pull_request:
-    branches:
-    - main
-    paths:
-    - '**.swift'
-    - '**.yml'
   workflow_dispatch:
 
 jobs:
-  macOS:
-    runs-on: macOS-latest
-    steps:
-    - name: Checkout
-      uses: actions/checkout@v2
-    - name: SPM tests
-      run: swift test
   linux:
     runs-on: ubuntu-latest
     strategy:
       matrix:
         image:
-          - 'swift:5.5-focal'
+          - 'swift:5.8'
+          - 'swift:5.9'
+          - 'swift:5.10'
     container:
       image: ${{ matrix.image }}
     steps: