Drop PULL_REQUEST column from COMMIT_COMMENT table

src/main/twirl/gitbucket/core/helper/commitcomment.scala.html

@@ -15,9 +15,9 @@
       @user(comment.commentedUserName, styleClass="username strong")
         <span class="muted">
           commented
-          @if(comment.pullRequest){
+          @if(comment.issueId.isDefined){
             on this Pull Request
-          }else{
+          } else {
             @if(comment.fileName.isDefined){
               on @comment.fileName.get
             }