fix(screenshot-capture): use dynamic getState to avoid stale state snapshot

[Sahitya0805]

Description

The ScreenshotCaptureSummary class was storing a snapshot of the Redux state in its constructor. This led to "metadata leakage" when a user switched conferences or when JWTs rotated, as the class continued to use the old state for subsequent screenshots.

This PR refactors the class to store a reference to the getState function instead, ensuring that every time a screenshot is processed, it retrieves the most current data from the store.

Fixes #17247

Checklist

• The title of the pull request follows the Conventional Commits specification.
• The description of the pull request is detailed and explains the "why" behind the changes.

[jitsi-jenkins]

Hi, thanks for your contribution!
If you haven't already done so, could you please make sure you sign our CLA (https://jitsi.org/icla for individuals and https://jitsi.org/ccla for corporations)? We would unfortunately be unable to merge your patch unless we have that piece :(.