Revert JRuby manifest timeout to 180s (CF platform maximum) (#1142)

PR #1140 changed the timeout from 180s to 300s, but CloudFoundry has a platform-wide maximum of 180s (cc.maximum_health_check_timeout: 180).

Deployment fails with:
  'health_check_timeout Maximum exceeded: max 180s'

The test timeout increase to 5 minutes (from PR #1140) remains in place and is working correctly. This change only reverts the manifest timeout to comply with the CF platform constraint.

With timeout: 180s and test polling: 5min, tests should pass in most cases. Some flakiness may remain on extremely slow CI workers, which is an acceptable tradeoff given the platform constraint.

Fixes deployment failures introduced by PR #1140.

Author: ivanovac

fixtures/default/sinatra_jruby/manifest.yml

@@ -2,4 +2,4 @@
 applications:
 - name: sinatra_jruby_web_app
   health-check-type: process
-  timeout: 300
+  timeout: 180