fix: Remove RefreshBootstrap and refresh token handling

[mofojed]

• This never worked and doesn't get used anyway, since we attempt re-login with the pre-shared key if provided
• Tested by logging into a server with a pre-shared key, then hitting Refresh and ensuring it logged in again without being prompted

[codecov[bot]]

Codecov Report

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

Project coverage is 46.61%. Comparing base (229adf0) to head (4560be7).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2257 +/- ## ========================================== + Coverage 46.57% 46.61% +0.04% ========================================== Files 698 696 -2 Lines 38767 38731 -36 Branches 9866 9802 -64 ========================================== Hits 18054 18054 + Misses 20702 20623 -79 - Partials 11 54 +43 ``` | [Flag](https://app.codecov.io/gh/deephaven/web-client-ui/pull/2257/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=deephaven) | Coverage Δ | | |---|---|---| | [unit](https://app.codecov.io/gh/deephaven/web-client-ui/pull/2257/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=deephaven) | `46.61% <ø> (+0.04%)` | :arrow_up: | 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=deephaven#carryforward-flags-in-the-pull-request-comment) to find out more.

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