dashboard: add known issue for linux-amd64-unified

For golang/go#52653.
Updates golang/go#52150.

Change-Id: Ie76101e2a790b77c85a89fe41f4069f8cdd1522d
Reviewed-on: https://go-review.googlesource.com/c/build/+/408699
Auto-Submit: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Alex Rakoczy <alex@golang.org>
diff --git a/dashboard/builders.go b/dashboard/builders.go
index e387251..6346f2f 100644
--- a/dashboard/builders.go
+++ b/dashboard/builders.go
@@ -1804,6 +1804,7 @@
 		},
 		numTestHelpers:    1,
 		numTryTestHelpers: 4,
+		KnownIssues:       []int{52150},
 	})
 	addBuilder(BuildConfig{
 		Name:     "linux-amd64-nounified",