[BEAM-12710] Disable TestStreamTest.testFirstElementLate for portable FlinkRunner

[je-ik]

Fixes [BEAM-12710]. I'm not sure if this should be considered a permanent fix, but I'd say that yes - the test will probably never function properly on Flink.

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ValidatesRunner compliance status (on master branch)

Lang	ULR	Dataflow	Flink	Samza	Spark	Twister2
Go	---					---
Java
Python	---					---
XLang						---

Examples testing status on various runners

Lang	ULR	Dataflow	Flink	Samza	Spark	Twister2
Go	---	---	---	---	---	---	---
Java	---		---	---	---	---	---
Python	---	---	---	---	---	---	---
XLang	---	---	---	---	---	---	---

Post-Commit SDK/Transform Integration Tests Status (on master branch)

Go	Java	Python

Pre-Commit Tests Status (on master branch)

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

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GitHub Actions Tests Status (on master branch)

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[je-ik]

Run Java Flink PortableValidatesRunner Streaming

[je-ik]

@kennknowles Would you have a sec to review this?

[je-ik]

R: @lukecwik

[lukecwik]

This mirrors the already disabled test in non-portable

beam/runners/flink/flink_runner.gradle

Line 245 in 8b6f675

excludeTestsMatching 'org.apache.beam.sdk.testing.TestStreamTest.testFirstElementLate'

so it makes sense to disable here.