ci: fixes versioning prefix to allow for numeric ordering of versions

Author: baywet

release-please-config.json

@@ -15,7 +15,7 @@
   "draft": false,
   "prerelease": true,
   "versioning": "prerelease",
-  "prerelease-type": "preview",
+  "prerelease-type": "preview.",
   "packages": {
     ".": {
       "package-name": "Microsoft.OpenApi",