Fix duplicate status check contexts (#30660)
Caused by #30076.
There may be some duplicate status check contexts when setting status
checks for a branch protection rule. The duplicate contexts should be
removed.
Before:
<img
src="https://github.com/go-gitea/gitea/assets/15528715/97f4de2d-4868-47a3-8a99-5a180f9ac0a3"
width="600px" />
After:
<img
src="https://github.com/go-gitea/gitea/assets/15528715/ff7289c5-9793-4090-ba31-e8cb3c85f8a3"
width="600px" />
(cherry picked from commit 7ad50313284db7eec565ad1750108de1444c5a84)
authored by