Bump actions/checkout from 3 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...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/ci.yml

@@ -18,7 +18,7 @@ jobs:
 
     steps:
       - name: Checkout ARC
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           path: ARC
 

.github/workflows/codeql.yml

@@ -24,7 +24,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v6
 
       - name: Initialize CodeQL
         uses: github/codeql-action/init@v3

.github/workflows/docker_build.yml

@@ -34,7 +34,7 @@ jobs:
           swap-storage: true
 
       - name: Checkout
-        uses: actions/checkout@v5.0.0
+        uses: actions/checkout@v6
 
       - name: Set up Buildx
         uses: docker/setup-buildx-action@v3.11.1

.github/workflows/gh-pages.yml

@@ -14,7 +14,7 @@ jobs:
     steps:
       # ── clone ARC repo ───────────────────────────────────────────
       - name: Checkout ARC
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: ReactionMechanismGenerator/ARC
           path: ARC

.github/workflows/update-cache.yml

@@ -19,7 +19,7 @@ jobs:
     steps:
       # ────────── source repo ──────────
       - name: Checkout ARC
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       # ────────── AutoTST ──────────
       - name: Cache AutoTST
@@ -32,7 +32,7 @@ jobs:
             ${{ runner.os }}-autotst-
       - name: Checkout AutoTST
         if: steps.cache-autotst.outputs.cache-hit != 'true'
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: ReactionMechanismGenerator/AutoTST
           path: AutoTST
@@ -50,7 +50,7 @@ jobs:
             ${{ runner.os }}-tsgcn-
       - name: Checkout TS-GCN
         if: steps.cache-tsgcn.outputs.cache-hit != 'true'
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: ReactionMechanismGenerator/TS-GCN
           path: TS-GCN
@@ -68,7 +68,7 @@ jobs:
             ${{ runner.os }}-kinbot-
       - name: Checkout KinBot 2.0.6
         if: steps.cache-kinbot.outputs.cache-hit != 'true'
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: zadorlab/KinBot
           path: KinBot