test: remove duplicate heartbeat event cleanup

Co-authored-by: Paperclip <noreply@paperclip.ing>

server/src/__tests__/heartbeat-retry-scheduling.test.ts

@@ -101,7 +101,6 @@ describeEmbeddedPostgres("heartbeat bounded retry scheduling", () => {
 
   async function cleanupRetryFixture() {
     await db.delete(activityLog);
-    await db.delete(heartbeatRunEvents);
     await db.delete(environmentLeases);
     await db.delete(issueRelations);
     await db.delete(issues);