Update settings_reset_prompt owners, metadata

Fun history for the owners and metadata of
c/b/safe_browsing/settings_reset_prompt:

OWNERS file:
- The OWNERS file originally specified owners [1]
- The OWNERS file then specified owners and a component,
  UI>Browser>Preferences>Protector [2]
- Then, the owners were removed from OWNERS (allowing it to inherit),
  but the component was kept. [3]
- Finally, the component was moved to DIR_METADATA, making the
  OWNERS file obsolete. [4]

Meanwhile, the DIR_METADATA file:
- When created, correctly specified the component [4]
- Eventually, the component was changed to Services>Safebrowsing. This
  is because UI>Browser>Preferences did not exist - even though
  UI>Browser>Preferences>Protector did. [5]
- Finally, the component was removed, because it was redundant with the
  parent directory. [6]

This left the owners file in a state where it simply said:

```
Inherit owners from the parent directory, but use a different component.
```

Despite neither it nor the DIR_METADATA file specifying a different component.

Remove the now-unnecessary owners file, and restore the component
(UI>Browser>Preferences>Protector), as it still exists in crbug.

[1] https://crrev.com/7a89d15
[2] https://crrev.com/021fec4
[3] https://crrev.com/a4df7e6
[4] https://crrev.com/dd89ec4
[5] https://crrev.com/cb833fd
[6] https://crrev.com/6dfb6d1

Bug: None
Change-Id: I794ceb847586dd0849c007fe7ea5f4c3c36c0123
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2945082
Reviewed-by: Varun Khaneja <vakh@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#892237}