Bump actions/checkout from 3 to 4 (#9)

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/part_docs.yml

@@ -26,7 +26,7 @@ jobs:
       MIX_ENV: dev
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: erlef/setup-beam@v1
         id: setupBEAM
         with:
@@ -66,7 +66,7 @@ jobs:
       contents: write
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/download-artifact@v3
         with:
           name: docs

.github/workflows/part_test.yml

@@ -23,7 +23,7 @@ jobs:
       MIX_ENV: dev
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: erlef/setup-beam@v1
         id: setupBEAM
         with:
@@ -69,7 +69,7 @@ jobs:
       MIX_ENV: test
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           submodules: 'true'
       - uses: erlef/setup-beam@v1
@@ -110,7 +110,7 @@ jobs:
       MIX_ENV: dev
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: erlef/setup-beam@v1
         id: setupBEAM
         with:
@@ -143,7 +143,7 @@ jobs:
       DIALYZER_PLT_PRIV: true
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: erlef/setup-beam@v1
         id: setupBEAM
         with:
@@ -188,7 +188,7 @@ jobs:
       DIALYZER_PLT_PRIV: true
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: erlef/setup-beam@v1
         id: setupBEAM
         with: