REFACTOR: removes useless conditional (#9674)

We already check if there's a post in the line before.

app/assets/javascripts/discourse/app/lib/link-lookup.js

@@ -20,12 +20,10 @@ export default class LinkLookup {
     if (linkInfo) {
       if (post) {
         // Skip edits to the OP
-        if (post) {
         const postNumber = post.get("post_number");
         if (postNumber === 1 || postNumber === linkInfo.post_number) {
           return NO_RESULT;
         }
-        }
 
         // Don't warn on older posts
         const createdAt = moment(post.get("created_at"));