fix(useActiveElement): use computedWithControl instead of counter ref

[vaakian]

Description

instead of creating a pointless counter ref to do the trigger and track,
this change is to reuse computedWithControl to trigger the document.activeElement update.

no any functionality change, just a better approach.

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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• Read the Contributing Guidelines.
• Read the Pull Request Guidelines.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[adrianjost]

This change unfortunately broke the useActiveElement implementation for Vue 2 applications, because the trigger of computedWithControl is only available in Vue3 environments. 😢