Bump the github-actions group with 2 updates

Bumps the github-actions group with 2 updates: [actions/upload-artifact](https://github.com/actions/upload-artifact) and [actions/download-artifact](https://github.com/actions/download-artifact).


Updates `actions/upload-artifact` from 6 to 7
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v6...v7)

Updates `actions/download-artifact` from 7 to 8
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v7...v8)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: github-actions
- dependency-name: actions/download-artifact
  dependency-version: '8'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: github-actions
...

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

Author: dependabot[bot]

.github/workflows/c_on_three_oses.yml

@@ -66,7 +66,7 @@ jobs:
           Path('result.txt').write_text(result_line)
       
       - name: Upload results
-        uses: actions/upload-artifact@v6
+        uses: actions/upload-artifact@v7
         with:
           name: result-${{ matrix.os }}-${{ matrix.ccompiler }}
           path: result.txt
@@ -76,7 +76,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Download all artifacts
-        uses: actions/download-artifact@v7
+        uses: actions/download-artifact@v8
         with:
           path: results
 
@@ -169,7 +169,7 @@ jobs:
           print(markdown_table)
       
       - name: Upload markdown table
-        uses: actions/upload-artifact@v6
+        uses: actions/upload-artifact@v7
         with:
           name: size-comparison-table
           path: size_comparison_table.md

.github/workflows/macOS_on_demand.yml

@@ -31,7 +31,7 @@ jobs:
     - name: Display ${{ matrix.os }}_cpu.md content
       run: cat ${{ matrix.os }}_cpu.md
     - name: Upload ${{ matrix.os }}_cpu.md artifact
-      uses: actions/upload-artifact@v6
+      uses: actions/upload-artifact@v7
       with:
         name: ${{ matrix.os }}_cpu
         path: ${{ matrix.os }}_cpu.md
@@ -65,7 +65,7 @@ jobs:
     steps:
     - uses: actions/checkout@v6
     - name: Download all CPU artifacts
-      uses: actions/download-artifact@v7
+      uses: actions/download-artifact@v8
       with:
         pattern: "*_cpu"
         merge-multiple: true
@@ -125,7 +125,7 @@ jobs:
         else:
             print("Contents are the same, no update needed")
     - name: Upload combined macOS_CPUs.md
-      uses: actions/upload-artifact@v6
+      uses: actions/upload-artifact@v7
       with:
         name: macOS_CPUs_final
         path: |