Update version for next patch release

Author: ephox

package.json

@@ -70,6 +70,6 @@
     "typescript": "~5.4.3",
     "vite": "^5.2.2"
   },
-  "version": "5.1.1",
+  "version": "5.1.2-rc",
   "name": "@tinymce/tinymce-react"
 }