chore(deps): 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/contracts.yml

@@ -16,7 +16,7 @@ jobs:
       run:
         working-directory: contracts
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           submodules: recursive
       - name: Install Foundry
@@ -38,7 +38,7 @@ jobs:
       run:
         working-directory: contracts
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           submodules: recursive
       - name: Install Foundry

.github/workflows/rust.yml

@@ -11,7 +11,7 @@ jobs:
 
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Install Bitcoin
         run: |

.github/workflows/sdk-npm.yml

@@ -11,7 +11,7 @@ jobs:
       run:
         working-directory: ./sdk
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: setup node
         uses: actions/setup-node@v6
         with:

.github/workflows/sdk.yml

@@ -13,7 +13,7 @@ jobs:
       run:
         working-directory: ./sdk
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Setup node
         uses: actions/setup-node@v6
         with: