build(deps): bump gittools/actions from 0.9.13 to 0.9.15

Bumps [gittools/actions](https://github.com/gittools/actions) from 0.9.13 to 0.9.15.
- [Release notes](https://github.com/gittools/actions/releases)
- [Commits](GitTools/actions@v0.9.13...v0.9.15)

---
updated-dependencies:
- dependency-name: gittools/actions
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/dotnet.yml

@@ -26,12 +26,12 @@ jobs:
     - name: Test
       run: dotnet test --no-build --verbosity normal
     - name: Install GitVersion
-      uses: gittools/actions/gitversion/[email protected].13
+      uses: gittools/actions/gitversion/[email protected].15
       with:
         versionSpec: '5.x'
     - name: Determine Version
       id: gitversion # step id used as reference for output values
-      uses: gittools/actions/gitversion/[email protected].13
+      uses: gittools/actions/gitversion/[email protected].15
     - name: Semantic Version
       run: |
         echo "SemVer: ${{ steps.gitversion.outputs.semVer }}"