fix(onboarding): use platform getPrBody

lib/workers/repository/onboarding/pr/index.js

@@ -62,6 +62,8 @@ You can post questions in [our Config Help repository](https://github.com/renova
   }
   logger.trace('prBody:\n' + prBody);
 
+  prBody = platform.getPrBody(prBody);
+
   // Check if existing PR exists
   const existingPr = await platform.getBranchPr(`renovate/configure`);
   if (existingPr) {