Fix: problem 테이블 중복 속성 제거 (#121)

- problem 테이블에 submission과 code_submission이 중복되어 발생한 경고에 대해서,
code_submission을 제거하여 해결했습니다.

Author: deveroskp

wacruit/src/admin/views.py

@@ -138,7 +138,6 @@ class ProblemAdmin(ModelView, model=Problem):
 
     form_excluded_columns = [
         Problem.submissions,
-        Problem.code_submissions,
         Problem.testcases,
     ]
 

wacruit/src/apps/problem/models.py

@@ -39,9 +39,6 @@ class Problem(DeclarativeBase):
     recruiting: Mapped["Recruiting"] = relationship(back_populates="problems")
     submissions: Mapped[list["CodeSubmission"]] = relationship(back_populates="problem")
     testcases: Mapped[list["Testcase"]] = relationship(back_populates="problem")
-    code_submissions: Mapped[list["CodeSubmission"]] = relationship(
-        back_populates="problem"
-    )
 
     def __str__(self) -> str:
         return f"<Problem id={self.id}, num={self.num}, body={self.body[:10]}..>"