[gh-actions](deps): Bump actions/upload-artifact from 5 to 6

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 5 to 6.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v5...v6)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  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/build-macos-arm64.yaml

@@ -131,7 +131,7 @@ jobs:
              git-annex_"${{ steps.build-version.outputs.version }}".dmg
 
       - name: Upload packages
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: git-annex-macos-arm64-dmg_${{ steps.build-version.outputs.version }}
           path: |

.github/workflows/build-macos.yaml

@@ -131,7 +131,7 @@ jobs:
              git-annex_"${{ steps.build-version.outputs.version }}".dmg
 
       - name: Upload packages
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: git-annex-macos-dmg_${{ steps.build-version.outputs.version }}
           path: |

.github/workflows/build-ubuntu.yaml

@@ -142,7 +142,7 @@ jobs:
         if: "!contains(env.DEB_BUILD_OPTIONS, 'nocheck')"
 
       - name: Upload packages
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: git-annex-debianstandalone-packages_${{ steps.build-version.outputs.version }}
           path: |

.github/workflows/build-windows.yaml

@@ -151,7 +151,7 @@ jobs:
              git-annex-installer_"${{ steps.build-version.outputs.version }}".exe
 
       - name: Upload packages
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: git-annex-windows-installer_${{ steps.build-version.outputs.version }}
           path: |