Reduce Java Examples Dataflow Precommit timeout

[Ardagan]

Current tests generally finish within 15 minutes. However if something goes wrong we wait for 2 hours for timeout. This is too big of overhead. Reducing timeout to 30 minutes.

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Post-Commit Tests Status (on master branch)

Lang	SDK	Apex	Dataflow	Flink	Gearpump	Samza	Spark
Go		---	---		---	---
Java
Python		---			---	---
XLang	---	---	---		---	---	---

Pre-Commit Tests Status (on master branch)

---	Java	Python	Go	Website
Non-portable
Portable	---		---	---

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[Ardagan]

R: @pabloem, @kennknowles

[pabloem]

Thanks. LGTM.

[Ardagan]

Run Seed Job