tests: Avoid actions' warnings

Author: jcs090218

.github/workflows/activate.yml

@@ -22,7 +22,7 @@ jobs:
           - 28.2
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - uses: jcs090218/setup-emacs@master
       with:

.github/workflows/test.yml

@@ -24,7 +24,7 @@ jobs:
           - snapshot
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - uses: jcs090218/setup-emacs@master
       with: