playground: update app.yaml

+ Use split health checks as specified in
  https://cloud.google.com/appengine/docs/flexible/go/configuring-your-app-with-app-yaml#updated_health_checks
+ Update instance types with more RAM and CPU cores

Change-Id: I1dad9994a2a0c0c2791e5e1425a6ccd524649512
Reviewed-on: https://go-review.googlesource.com/90675
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/app.yaml b/app.yaml
index 77cba63..c6791f8 100644
--- a/app.yaml
+++ b/app.yaml
@@ -2,13 +2,16 @@
 runtime: custom
 env: flex
 
+resources:
+  cpu: 2
+  memory_gb: 2
+
 automatic_scaling:
   min_num_instances: 5
-  max_num_instances: 20
 
-health_check:
-  check_interval_sec: 20
-  restart_threshold: 10
+readiness_check:
+  path: "/_ah/health"
+  check_interval_sec: 10
 
 env_variables:
   MEMCACHED_ADDR: 'memcached:11211'