build(deps): bump gitversion.tool to 6.8.1 (#928)

---
updated-dependencies:
- dependency-name: gitversion.tool
  dependency-version: 6.8.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]

.config/dotnet-tools.json

@@ -3,7 +3,7 @@
   "isRoot": true,
   "tools": {
     "gitversion.tool": {
-      "version": "6.7.0",
+      "version": "6.8.1",
       "commands": [
         "dotnet-gitversion"
       ],