Roll back actions/checkout action to v4.0.0

| datasource  | package          | from | to     |
| ----------- | ---------------- | ---- | ------ |
| github-tags | actions/checkout | v4   | v4.0.0 |


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

Author: renovate[bot]

.github/workflows/backward-compatibility-check.yml

@@ -22,7 +22,7 @@ jobs:
 
     steps:
       - name: "Checkout"
-        uses: actions/checkout@v4
+        uses: actions/checkout@v4.0.0
         with:
           fetch-depth: 0
 

.github/workflows/coding-standard.yml

@@ -29,7 +29,7 @@ jobs:
 
         steps:
             - name: "Checkout"
-              uses: actions/checkout@v4
+              uses: actions/checkout@v4.0.0
 
             - name: "Install PHP"
               uses: "shivammathur/setup-php@2.24.0"

.github/workflows/mutation-tests.yml

@@ -29,7 +29,7 @@ jobs:
 
         steps:
             - name: "Checkout"
-              uses: actions/checkout@v4
+              uses: actions/checkout@v4.0.0
 
             - name: "Install PHP"
               uses: "shivammathur/setup-php@2.24.0"

.github/workflows/phpstan.yml

@@ -29,7 +29,7 @@ jobs:
 
         steps:
             - name: "Checkout"
-              uses: actions/checkout@v4
+              uses: actions/checkout@v4.0.0
 
             - name: "Install PHP"
               uses: "shivammathur/setup-php@2.24.0"

.github/workflows/psalm.yml

@@ -29,7 +29,7 @@ jobs:
 
         steps:
             - name: "Checkout"
-              uses: actions/checkout@v4
+              uses: actions/checkout@v4.0.0
 
             - name: "Install PHP"
               uses: "shivammathur/setup-php@2.24.0"

.github/workflows/release-on-milestone-closed-triggering-release-event.yml

@@ -18,7 +18,7 @@ jobs:
 
         steps:
             - name: "Checkout"
-              uses: actions/checkout@v4
+              uses: actions/checkout@v4.0.0
 
             - name: "Release"
               uses: "laminas/automatic-releases@v1"

.github/workflows/unit.yml

@@ -38,7 +38,7 @@ jobs:
 
         steps:
             - name: "Checkout"
-              uses: actions/checkout@v4
+              uses: actions/checkout@v4.0.0
 
             - name: "Install PHP"
               uses: "shivammathur/setup-php@2.24.0"