Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/aosus-wordpress.yml

@@ -16,7 +16,7 @@ jobs:
       url: https://aosus.org
     steps:
       - name: checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/caddy.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/discourse-db.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/discourse.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/docker-mailserver.yml

@@ -15,7 +15,7 @@ jobs:
       name: Docker-mailserver
     steps:
       - name: checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/matrix.yml

@@ -16,7 +16,7 @@ jobs:
       url: https://matrix.aosus.org
     steps:
       - name: checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/plausible.yml

@@ -16,7 +16,7 @@ jobs:
       url: https://pa.aosus.org
     steps:
       - name: checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/pr-test.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Install Compose
         uses: ndeloof/install-compose-action@v0.0.1