[BEAM-8375]Correct the command for Start a Flink job server in `envir…

[sunjincheng121]

Correct the command for Start a Flink job server in environments.md.
./gradlew :runners:flink:1.5:job-server:runShadow to ./gradlew :runners:flink:1.7:job-server:runShadow

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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	---		---	---

See .test-infra/jenkins/README for trigger phrase, status and link of all Jenkins jobs.

[sunjincheng121]

Missing by #9632

[sunjincheng121]

R: @mxm

[mxm]

Thanks. We need to come up with a sensible way to auto-update these references.