Fix fleet dashboard page's scroll bar

[momesgin]

Summary

Fixes #10632

Occurred changes and/or fixed issues

Technical notes summary

Removed unnecessary class .fleet-dashboard as it wasn't referenced anywhere else, and its min-height: 100vh styling was causing the issue. Note that you would only see the scroll bar if you had the os setting enabled to always show the scroll bars:

Areas or cases that should be tested

Try different browsers and turn on the os setting mentioned above.

Areas which could experience regressions

I've already tried different pages on the fleet section and couldn't find any regression there, but would be good if a second person test it too.

Screenshot/Video

Checklist

• The PR is linked to an issue and the linked issue has a Milestone, or no issue is needed
• The PR has a Milestone
• The PR template has been filled out
• The PR has been self reviewed
• The PR has a reviewer assigned
• The PR has automated tests or clear instructions for manual tests and the linked issue has appropriate QA labels, or tests are not needed
• The PR has reviewed with UX and tested in light and dark mode, or there are no UX changes

[eva-vashkevich]

lgtm