[BUGFIX] `argilla frontend`: Avoid call router.push when opening an external URL

[frascuchon]

Description

This PR fixes the router.go method and avoids calling router.push when the external flag is True

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested

Checklist

• I added relevant documentation
• I followed the style guidelines of this project
• I did a self-review of my code
• I made corresponding changes to the documentation
• I confirm My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have added relevant notes to the CHANGELOG.md file (See https://keepachangelog.com/)

[github-actions[bot]]

The URL of the deployed environment for this PR is https://argilla-quickstart-pr-5675-ki24f765kq-no.a.run.app

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.08%. Comparing base (229809e) to head (78a8536).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #5675 +/- ## =========================================== - Coverage 91.10% 91.08% -0.02% =========================================== Files 150 150 Lines 6250 6250 =========================================== - Hits 5694 5693 -1 - Misses 556 557 +1 ``` | [Flag](https://app.codecov.io/gh/argilla-io/argilla/pull/5675/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=argilla-io) | Coverage Δ | | |---|---|---| | [argilla-server](https://app.codecov.io/gh/argilla-io/argilla/pull/5675/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=argilla-io) | `91.08% <ø> (-0.02%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=argilla-io#carryforward-flags-in-the-pull-request-comment) to find out more.

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