Bump actions/checkout from 5 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/python-ci-pr.yaml

@@ -31,7 +31,7 @@ jobs:
         uses: frequenz-floss/gh-action-setup-git@v1.0.0
 
       - name: Fetch sources
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           submodules: true
 
@@ -59,7 +59,7 @@ jobs:
         uses: frequenz-floss/gh-action-setup-git@v1.0.0
 
       - name: Fetch sources
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           submodules: true
 

.github/workflows/python-ci.yaml

@@ -107,7 +107,7 @@ jobs:
         uses: frequenz-floss/gh-action-setup-git@v1.0.0
 
       - name: Fetch sources
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           submodules: true
 
@@ -153,7 +153,7 @@ jobs:
         uses: frequenz-floss/gh-action-setup-git@v1.0.0
 
       - name: Fetch sources
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           submodules: true
 
@@ -189,7 +189,7 @@ jobs:
         uses: frequenz-floss/gh-action-setup-git@v1.0.0
 
       - name: Fetch sources
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           submodules: true
 

.github/workflows/release.yaml

@@ -13,7 +13,7 @@ jobs:
         run: env
 
       - name: Fetch sources
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           submodules: recursive
 
@@ -67,7 +67,7 @@ jobs:
     permissions:
       id-token: write
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: rust-lang/crates-io-auth-action@b7e9a28eded4986ec6b1fa40eeee8f8f165559ec  # v1.0.3
         id: auth
       - run: cargo publish

.github/workflows/rust-ci.yaml

@@ -22,7 +22,7 @@ jobs:
 
     steps:
       - name: Fetch sources
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           submodules: recursive