Bump actions/checkout from 2 to 2.3.4

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 2.3.4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v2...v2.3.4)

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/api-integration-tests.yml

@@ -46,7 +46,7 @@ jobs:
             nextcloud: 17
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v2.3.4
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2

.github/workflows/api-php-static-code-check.yml

@@ -13,7 +13,7 @@ jobs:
     name: "phpstan: Nextcloud ${{ matrix.nextcloud }}"
     steps:
       - name: Checkout
-        uses: actions/checkout@master
+        uses: actions/checkout@v2.3.4
       - name: Set up php
         uses: shivammathur/setup-php@master
         with:

.github/workflows/api-php-tests.yml

@@ -15,7 +15,7 @@ jobs:
         experimental: [false]
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v2.3.4
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2

.github/workflows/build-release.yml

@@ -19,7 +19,7 @@ jobs:
         database: ['sqlite']
     steps:
       - name: Checkout
-        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f
+        uses: actions/checkout@v2.3.4
 
       - name: Setup PHP
         uses: shivammathur/setup-php@afefcaf556d98dc7896cca380e181decb609ca44

.github/workflows/changelog-enforcer.yml

@@ -8,7 +8,7 @@ jobs:
   changelog:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v2.3.4
     - uses: dangoslen/changelog-enforcer@v2.2.0
       with:
         changeLogPath: 'CHANGELOG.md'

.github/workflows/frontend-nodejs-tests.yml

@@ -15,7 +15,7 @@ jobs:
         experimental: [false]
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v2.3.4
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2

.github/workflows/post-merge-tasks.yml

@@ -20,7 +20,7 @@ jobs:
         nextcloud: ['stable21']
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v2.3.4
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2