internal/worker: speed up task creation by 2x

As of July 24th, enqueueAll endpoint is exceeding its time deadline. It
gets retried successfully, but it should not be failing anyhow. This CL
attempts to accomplish that.

Change-Id: I70f409201ea1dc58e2be815f7321568f7aa13e18
Reviewed-on: https://go-review.googlesource.com/c/pkgsite-metrics/+/521915
Run-TryBot: Zvonimir Pavlinovic <zpavlinovic@google.com>
Reviewed-by: Maceo Thompson <maceothompson@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
diff --git a/internal/worker/enqueue.go b/internal/worker/enqueue.go
index 7cfa9a6..24f2c58 100644
--- a/internal/worker/enqueue.go
+++ b/internal/worker/enqueue.go
@@ -40,7 +40,7 @@
 	defer derrors.Wrap(&err, "enqueueTasks")
 
 	// Enqueue concurrently, because sequentially takes a while.
-	const concurrentEnqueues = 10
+	const concurrentEnqueues = 20
 	var (
 		mu                 sync.Mutex
 		nEnqueued, nErrors int