Bump Github Actions version to v3

Node12 and as a result Github Actions v2 will apparently soon be
deprecated, see: https://github.blog/changelog/2023-06-13-github-actions-all-actions-will-run-on-node16-instead-of-node12-by-default/
Thus this changes all workflow jobs to use `actions/checkout@v3`.

Signed-off-by: Sandro-Alessio Gierens <sandro@gierens.de>
diff --git a/.github/workflows/coverity.yml b/.github/workflows/coverity.yml
index b383317..a81da86 100644
--- a/.github/workflows/coverity.yml
+++ b/.github/workflows/coverity.yml
@@ -9,7 +9,7 @@
     timeout-minutes: 5
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: run-scan
         run: |
           sudo apt-get update
diff --git a/.github/workflows/pull_request.yml b/.github/workflows/pull_request.yml
index 3b99a28..d8323e3 100644
--- a/.github/workflows/pull_request.yml
+++ b/.github/workflows/pull_request.yml
@@ -5,7 +5,7 @@
     timeout-minutes: 10
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: pre-push
         run: |
           sudo apt-get update
@@ -17,7 +17,7 @@
     timeout-minutes: 10
     runs-on: ubuntu-22.04
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: pre-push
         run: |
           sudo apt-get update
@@ -30,7 +30,7 @@
     runs-on: ubuntu-latest
     container: centos:7
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: pre-push
         run: |
           # NB: no working flake8
@@ -43,7 +43,7 @@
     runs-on: ubuntu-latest
     container: fedora:35
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: pre-push
         run: |
           dnf -y install --releasever=35 \
@@ -55,6 +55,6 @@
     runs-on: ubuntu-latest
     container: vlajos/misspell-fixer
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: run misspell-fixer
         run: /misspell-fixer/misspell-fixer -sv .