chore(be): remove duplicated import lines

apps/backend/apps/admin/src/problem/problem.service.ts

@@ -1,6 +1,5 @@
 import { CACHE_MANAGER } from '@nestjs/cache-manager'
 import { Cache } from '@nestjs/cache-manager'
-import { Inject, Injectable } from '@nestjs/common'
 import {
   Inject,
   Injectable,
@@ -11,8 +10,8 @@ import { Language } from '@generated'
 import type { ContestProblem, Tag, WorkbookProblem } from '@generated'
 import { Level } from '@generated'
 import type { ProblemWhereInput } from '@generated'
-import { randomUUID } from 'crypto'
 import { Prisma } from '@prisma/client'
+import { randomUUID } from 'crypto'
 import { Workbook } from 'exceljs'
 import type { ReadStream } from 'fs'
 import { MAX_IMAGE_SIZE } from '@libs/constants'