Bump actions/checkout from 3 to 4

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] <[email protected]>

Author: dependabot[bot]

.github/workflows/backward_compatibility.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: setup
       run: |
          command="sudo apt-get -y update && \

.github/workflows/heat_transfer_ci.yml

@@ -15,7 +15,7 @@ jobs:
     timeout-minutes: 30
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: run test
 
       run: |

.github/workflows/indent.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - uses: DoozyX/[email protected]
       with:
         source: '.'

.github/workflows/solid_mechanics_ci.yml

@@ -15,7 +15,7 @@ jobs:
     timeout-minutes: 60
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: run test
 
       run: |