Attempt to fix CI.

This change attempts to fix the following issues:
- cask setup fails on Emacs 24
- setup fails on macos, which was used to test bash 3.

by removing tests for Emacs 24 and Bash 3. There is no point in
supporting such old versions anymore.

Author: szermatt

.github/workflows/test.yml

@@ -9,13 +9,12 @@ jobs:
     strategy:
       matrix:
         emacs_version:
-          - '24.3'
-          - '25.1'
           - '25.3'
-          - '26.1'
-          - '26.2'
           - '26.3'
           - '27.1'
+          - '27.2'
+          - '28.1'
+          - '28.2'
           - 'snapshot'
         include:
           - emacs_version: 'snapshot'
@@ -35,12 +34,16 @@ jobs:
       if: matrix.allow_failure == true
       run: 'cask && make test || true'
 
-  test-macos-bash3:
-    runs-on: macos-10.15
+  test:
+    runs-on: ubuntu-20.04 # bash 5.0
     strategy:
       matrix:
         emacs_version:
-          - '26.3'
+          - '28.2'
+          - 'snapshot'
+        include:
+          - emacs_version: 'snapshot'
+            allow_failure: true
     steps:
     - uses: actions/checkout@v1
     - uses: purcell/setup-emacs@master
@@ -49,5 +52,9 @@ jobs:
     - uses: conao3/setup-cask@master
 
     - name: Run tests
+      if: matrix.allow_failure != true
       run: 'cask && make test'
-      
+
+    - name: Run tests (allow failure)
+      if: matrix.allow_failure == true
+      run: 'cask && make test || true'