playground: fix service name for app.goprev.yaml

Change-Id: I7c3650c91e69af42a63212dc6c8f07ae9b39ef81
Reviewed-on: https://go-review.googlesource.com/c/playground/+/367894
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
Reviewed-by: Alexander Rakoczy <alex@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
diff --git a/app.goprev.yaml b/app.goprev.yaml
index 2b19ccf..25eb285 100644
--- a/app.goprev.yaml
+++ b/app.goprev.yaml
@@ -1,4 +1,4 @@
-service: golast-play
+service: goprevplay
 runtime: custom
 env: flex