Remove nanostack border router from examples list

[adbridge]

Summary of changes

nanostack border router is now owned by ISG and has been moved out of ARMmbed and into their organisation. ISG will be
responsible for updating and testing this example going forward.

Impact of changes

nanostack-border-router example will no longer be tested in the mbed-os CI and will not automatically have
its mbed-os version updated whenever a release of mbed-os is made.

Migration actions required

None

Documentation

No updates required

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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

[x] No Tests required for this change (E.g docs only update)
[] 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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[ciarmcom]

@adbridge, thank you for your changes.
@ARMmbed/mbed-os-tools @ARMmbed/mbed-os-maintainers please review.

[0xc0170]

CI started

[mbed-ci]

Jenkins CI Test : ✔️ SUCCESS

Build Number: 1 | 🔒 Jenkins CI Job | 🌐 Logs & Artifacts

CLICK for Detailed Summary

jobs	Status
jenkins-ci/mbed-os-ci_unittests	✔️
jenkins-ci/mbed-os-ci_build-greentea-GCC_ARM	✔️
jenkins-ci/mbed-os-ci_build-example-ARM	✔️
jenkins-ci/mbed-os-ci_build-cloud-example-ARM	✔️
jenkins-ci/mbed-os-ci_build-greentea-ARM	✔️
jenkins-ci/mbed-os-ci_cmake-example-ARM	✔️
jenkins-ci/mbed-os-ci_build-example-GCC_ARM	✔️
jenkins-ci/mbed-os-ci_build-cloud-example-GCC_ARM	✔️
jenkins-ci/mbed-os-ci_cmake-example-GCC_ARM	✔️
jenkins-ci/mbed-os-ci_dynamic-memory-usage	✔️
jenkins-ci/mbed-os-ci_cloud-client-pytest	✔️
jenkins-ci/mbed-os-ci_greentea-test	✔️
jenkins-ci/mbed-os-ci_cmake-example-test	✔️