Fixed PR number

Author: Rhythm1710

src/bors/handlers/review.rs

@@ -145,7 +145,11 @@ pub(super) async fn command_close_tree(
         repo_state.repository(),
         TreeState::Closed {
             priority,
-            source: format!("https://github.com/{}/pull/1", repo_state.repository()),
+            source: format!(
+                "https://github.com/{}/pull/{}",
+                repo_state.repository(),
+                pr.number
+            ),
         },
     )
     .await?;
@@ -479,7 +483,11 @@ mod tests {
                     repo.unwrap().tree_state,
                     TreeState::Closed {
                         priority: 5,
-                        source: format!("https://github.com/{}/pull/1", default_repo_name()),
+                        source: format!(
+                            "https://github.com/{}/pull/{}",
+                            default_repo_name(),
+                            default_pr_number()
+                        ),
                     }
                 );