[argparse] Update to v2.8

[p-ranav]

Describe the pull request

• What does your PR fix?

Updates argparse to v2.8

• Which triplets are supported/not supported? Have you updated the CI baseline?

No

• Does your PR follow the maintainer guide?

Yes

• If you have added/updated a port: Have you run ./vcpkg x-add-version --all and committed the result?

Yes

If you are still working on the PR, open it as a Draft: https://github.blog/2019-02-14-introducing-draft-pull-requests/

[JonLiu1993]

/azp run

[azure-pipelines[bot]]

Azure Pipelines successfully started running 1 pipeline(s).

[JonLiu1993]

@p-ranav, CI for x64-linux is broken.

[p-ranav]

@JonLiu1993 The CI error seems to be unrelated to argparse?

========================== Starting Command Output ===========================
/usr/bin/pwsh -NoLogo -NoProfile -NonInteractive -Command . '/agent/_work/_temp/a002a5c9-eaa0-4d2f-b805-7c9d838cda82.ps1'
Build reason was Pull Request, using binary caching in read write mode, skipping failures.
Clearing contents of /mnt/vcpkg-ci/buildtrees
Failure to remove_all_inside("/mnt/vcpkg-ci/buildtrees") due to file "/mnt/vcpkg-ci/buildtrees/tensorflow/.bzl/02c0d9509a4399b7d0b466397e539271/sandbox/inaccessibleHelperDir": Permission denied
Exception: /agent/_work/1/s/scripts/azure-pipelines/test-modified-ports.ps1:133
Line |
 133 |      throw "vcpkg clean failed"
     |      ~~~~~~~~~~~~~~~~~~~~~~~~~~
     | vcpkg clean failed

##[error]PowerShell exited with code '1'.
##[error]PowerShell wrote one or more lines to the standard error stream.
##[error]Exception: /agent/_work/1/s/scripts/azure-pipelines/test-modified-ports.ps1:133
Line |
 133 |      throw "vcpkg clean failed"
     |      ~~~~~~~~~~~~~~~~~~~~~~~~~~
     | vcpkg clean failed

I see a Permission denied on an unrelated package (tensorflow)

Failure to remove_all_inside("/mnt/vcpkg-ci/buildtrees") due to file "/mnt/vcpkg-ci/buildtrees/tensorflow/.bzl/02c0d9509a4399b7d0b466397e539271/sandbox/inaccessibleHelperDir": Permission denied