Adds remove option to ac table in rewards

[NejcZdovc]

Resolves brave/brave-browser#1379

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.
• Add appropriate QA labels (QA/Yes or QA/No) to include the closed issue in milestone

Test Plan:

1. clean profile
2. enable rewards
3. visit some site (wait on it for 10s)
4. go back to rewards settings
5. make sure that X is there and you can remove site

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

[ryanml]

++

[NejcZdovc]

master 443e6a8
0.56.x e15792e
0.55.x 08f15f0

[bsclifton]

Added merged/0.55.x label 😄

[NejcZdovc]

@bsclifton thx for adding the label, please keep rewards tags on the PR