Update actions/checkout action to v7 (#100)

| datasource  | package          | from | to     |
| ----------- | ---------------- | ---- | ------ |
| github-tags | actions/checkout | v6   | v7.0.0 |

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/ci.yml

@@ -20,7 +20,7 @@ jobs:
           - "8.4"
 
     steps:
-      - uses: "actions/checkout@v6"
+      - uses: "actions/checkout@v7"
       - uses: "shivammathur/setup-php@v2"
         with:
           coverage: "none"
@@ -41,7 +41,7 @@ jobs:
           - "8.5"
 
     steps:
-      - uses: "actions/checkout@v6"
+      - uses: "actions/checkout@v7"
       - uses: "shivammathur/setup-php@v2"
         with:
           coverage: "pcov"
@@ -64,7 +64,7 @@ jobs:
           - "8.4"
 
     steps:
-      - uses: "actions/checkout@v6"
+      - uses: "actions/checkout@v7"
       - uses: "shivammathur/setup-php@v2"
         with:
           coverage: "pcov"
@@ -94,7 +94,7 @@ jobs:
           - "8.4"
 
     steps:
-      - uses: "actions/checkout@v6"
+      - uses: "actions/checkout@v7"
       - uses: "shivammathur/setup-php@v2"
         with:
           coverage: "none"
@@ -116,7 +116,7 @@ jobs:
           - "8.4"
 
     steps:
-      - uses: "actions/checkout@v6"
+      - uses: "actions/checkout@v7"
       - uses: "shivammathur/setup-php@v2"
         with:
           coverage: "none"