internal/worker: update sandbox error categorization

"runner" prefix is not needed and will result in missed categorization.
The only thing that can cause "exit status 137" is the sandbox so we can
just use that string for matching. Instance failure with exit status 137
would not even give us a change to categorize an error.

Change-Id: Iaab892e8600c0ff91a73bd813fa7f6d58b637813
Reviewed-on: https://go-review.googlesource.com/c/pkgsite-metrics/+/552717
Reviewed-by: Maceo Thompson <maceothompson@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Run-TryBot: Zvonimir Pavlinovic <zpavlinovic@google.com>
diff --git a/internal/worker/scan.go b/internal/worker/scan.go
index 1c50455..4021310 100644
--- a/internal/worker/scan.go
+++ b/internal/worker/scan.go
@@ -369,6 +369,5 @@
 }
 
 func isSandboxRelatedIssue(err error) bool {
-	e := err.Error()
-	return strings.Contains(e, "runner") && strings.Contains(e, "status 137")
+	return strings.Contains(err.Error(), "exit status 137")
 }