Get repo assignees and reviewers should ignore deactivated users (#30770) (#30782)

Backport  #30770

If an user is deactivated, it should not be in the list of users who are
suggested to be assigned or review-requested.

old assignees or reviewers are not affected.

---
*Sponsored by Kithara Software GmbH*

(cherry picked from commit 022eac4ac8e59f861237cc1e02f7ef117eaf8e30)

Conflicts:
	models/repo/user_repo_test.go
	because there is one less fixture user compared to Gitea

tests/integration/api_repo_test.go

@@ -684,7 +684,9 @@ func TestAPIRepoGetReviewers(t *testing.T) {
 	resp := MakeRequest(t, req, http.StatusOK)
 	var reviewers []*api.User
 	DecodeJSON(t, resp, &reviewers)
-	assert.Len(t, reviewers, 4)
+	if assert.Len(t, reviewers, 3) {
+		assert.ElementsMatch(t, []int64{1, 4, 11}, []int64{reviewers[0].ID, reviewers[1].ID, reviewers[2].ID})
+	}
 }
 
 func TestAPIRepoGetAssignees(t *testing.T) {