fix(测试跟踪): 首页缺陷统计重复

--bug=1008738 --user=lyh
【测试跟踪】首页缺陷统计，测试计划列表里统计重复的问题
https://www.tapd.cn/55049933/s/1079772

backend/src/main/java/io/metersphere/base/mapper/ext/ExtTestCaseMapper.xml

@@ -440,7 +440,7 @@
         group by tc.maintainer
     </select>
     <select id="getTestPlanBug" resultType="int">
-        select count(tci.issues_id) from test_plan_test_case tptc join test_case_issues tci on tptc.case_id = tci.test_case_id join issues on tci.issues_id  = issues.id
+        select count(distinct (tci.issues_id)) from test_plan_test_case tptc join test_case_issues tci on tptc.case_id = tci.test_case_id join issues on tci.issues_id  = issues.id
         where tptc.plan_id = #{planId} and (issues.status != 'closed' or issues.status is null);
     </select>
     <select id="getTestPlanCase" resultType="int">