threads: fix timeout (set to 25)

[0xc0170]

Summary of changes

This fixes latest master testing (affects all Prs as of today), we should review and integrate asap.

To fix this issue: [1583145599.75][HTST][INF] test suite run finished after 20.04 sec...

Increase to leave some margin. This was observed in the latest master today with multiple
targets.

Impact of changes

Migration actions required

Documentation

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Pull request type

[X] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

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Test results

[] No Tests required for this change (E.g docs only update)
[X] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

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Reviewers

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@ARMmbed/mbed-os-core

[0xc0170]

The test currently takes ~20 seconds, at its limit so failing often this week.

[0xc0170]

I started CI to confirm this fixes it

[0xc0170]

I accidentally pushed , so have to restart testing

[mbed-ci]

Test run: FAILED

Summary: 3 of 4 test jobs failed
Build number : 1
Build artifacts

Failed test jobs:

• jenkins-ci/mbed-os-ci_build-ARM
• jenkins-ci/mbed-os-ci_build-GCC_ARM
• jenkins-ci/mbed-os-ci_build-IAR

[jamesbeyond]

LGTM, the timeout was a bit short

[mbed-ci]

Test run: SUCCESS

Summary: 5 of 5 test jobs passed
Build number : 2
Build artifacts