refactor: min coverage 기준 75로 낮춤.

- report는 exclude class 지정이 불가능하기 때문에, 해당 부분을 감안하여 커버리지 비율 조정

Related: #68

.github/workflows/ci.yml

@@ -41,7 +41,7 @@ jobs:
         with:
           paths: ${{ github.workspace }}/build/reports/jacoco/test/jacocoTestReport.xml
           token: ${{ secrets.GITHUB_TOKEN }}
-          min-coverage-overall: 80
-          min-coverage-changed-files: 80
+          min-coverage-overall: 75
+          min-coverage-changed-files: 75
           title: "⭐️Code Coverage"
           update-comment: true