Bump docfx from 2.77.0 to 2.78.0

Bumps [docfx](https://github.com/dotnet/docfx) from 2.77.0 to 2.78.0.
- [Release notes](https://github.com/dotnet/docfx/releases)
- [Changelog](https://github.com/dotnet/docfx/blob/main/RELEASENOTE.md)
- [Commits](dotnet/docfx@v2.77.0...v2.78.0)

---
updated-dependencies:
- dependency-name: docfx
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

.config/dotnet-tools.json

@@ -24,7 +24,7 @@
       "rollForward": false
     },
     "docfx": {
-      "version": "2.77.0",
+      "version": "2.78.0",
       "commands": [
         "docfx"
       ],