bug: fix assignees double load bug (#10856)

Because the assigness has been loaded in

compare.go 416:
    RetrieveRepoMetas(ctx, ctx.Repo.Repository, true)
then
issue.go 381
	RetrieveRepoMilestonesAndAssignees(ctx, repo)
then

issue.go 361 -- 365 , they are load assignees

So the code on compare.go 425 -- 427 is double work,
and which is the reason of #10853

Signed-off-by: a1012112796 <1012112796@qq.com>

routers/repo/compare.go

@@ -422,10 +422,6 @@ func CompareDiff(ctx *context.Context) {
 	beforeCommitID := ctx.Data["BeforeCommitID"].(string)
 	afterCommitID := ctx.Data["AfterCommitID"].(string)
 
-	if ctx.Data["Assignees"], err = ctx.Repo.Repository.GetAssignees(); err != nil {
-		ctx.ServerError("GetAssignees", err)
-		return
-	}
 
 	ctx.Data["Title"] = "Comparing " + base.ShortSha(beforeCommitID) + "..." + base.ShortSha(afterCommitID)