Removes a bad workaround for an issue that was introduced in 16.0

[diegoreymendez]

This is the first step to fixing: #15256

Rolls back a workaround I added for an issue with the refresh control in the list of sites.

My workaround was only hiding the refresh wheel, but it wasn't a proper fix for the problem, as the first row in the list of sites couldn't be selected by users.

Additional information

After rolling back these changes, we still need to fix the issue, which was introduced in this PR:

#15081

And specifically by this commit:

3a9543c

To test:

1. Run the App.
2. Switch to the "My Sites" tab.
3. If the refreshing activity wheel isn't visible on top of the first row, just tap on a site to see it's details, and go back to the list of sites.

Make sure you can see the refresh activity wheel on top of the first site (in the list of sites). As mentioned above, we need another PR to fix the underlying issue.

PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[peril-wordpress-mobile]

You can trigger an installable build for these changes by visiting CircleCI here.

[peril-wordpress-mobile]

You can trigger optional UI/connected tests for these changes by visiting CircleCI here.

[ScoutHarris]

Thanks @diegoreymendez !

[diegoreymendez]

Thanks for the review!