Meta: (test.yml) Update Emacs version matrix

We no longer support 26.3, and 27.2 is the latest of that series.

Author: alphapapa

.github/workflows/test.yml

@@ -41,8 +41,7 @@ jobs:
       fail-fast: false
       matrix:
         emacs_version:
-          - 26.3
-          - 27.1
+          - 27.2
           - 28.2
           - 29.1
           - snapshot