dashboard: remove known issue from openbsd-mips64-jsing builder

The openbsd/mips64 port is now functional and stable.

Fixes golang/go#40995

Change-Id: I959e6ab53777a3e048d89434f60aec365b0900b4
Reviewed-on: https://go-review.googlesource.com/c/build/+/275333
Trust: Joel Sing <joel@sing.id.au>
Reviewed-by: Alexander Rakoczy <alex@golang.org>

dashboard/builders.go

@@ -2083,7 +2083,6 @@ func init() {
 		Name:         "openbsd-mips64-jsing",
 		HostType:     "host-openbsd-mips64-joelsing",
 		SkipSnapshot: true,
-		KnownIssue:   40995,
 		buildsRepo: func(repo, branch, goBranch string) bool {
 			switch repo {
 			case "go", "net", "sys":