chore(deps): update dependency docfx to v2.78.4

Author: renovate-bot

.config/dotnet-tools.json

@@ -3,7 +3,7 @@
   "isRoot": true,
   "tools": {
     "docfx": {
-      "version": "2.78.3",
+      "version": "2.78.4",
       "commands": [
         "docfx"
       ]