Update actions in docs

Author: laupow

.github/workflows/test.yml

@@ -13,7 +13,7 @@ jobs:
 #  test: # make sure the action works on a clean machine without building
 #    runs-on: ubuntu-latest
 #    steps:
-#      - uses: actions/checkout@v3
+#      - uses: actions/checkout@v4
 #      - uses: ./
 #        with:
 #          milliseconds: 1000

README.md

@@ -51,7 +51,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Compile firmware
       id: compile