chore: Simplify by returning directly (#2627)

Author: KATO-Hiro

src/lib/services/contest_task_pairs.ts

@@ -23,16 +23,14 @@ export async function getContestTaskPair(
   contestId: string,
   taskId: string,
 ): Promise<ContestTaskPair | null> {
-  const contestTaskPair = await db.contestTaskPair.findUnique({
+  return await db.contestTaskPair.findUnique({
     where: {
       contestId_taskId: {
         contestId,
         taskId,
       },
     },
   });
-
-  return contestTaskPair;
 }
 
 /**