Fixed about:brave copy to clipboard tooltip

[cndouglas]

Old title: about:brave copy to clipboard tooltip is not working #8199 (comment)

Test Plan:

#8201 (comment)

1. Open about:brave with kabob > Help > About Brave.
2. Hover over the copy to clipboard button as shown in the screenshot below.
3. Make sure the tooltip Copy to clipboard tooltip is shown.

Original issue description

• Did you search for similar issues before submitting this one?
  Yes.

• Describe the issue you encountered:
  On the about:brave page, if you hover over the copy to clipboard button, it does not show the tooltip.

• Platform (Win7, 8, 10? macOS? Linux distro?):
  All.

• Brave Version (revision SHA):
  0.14.1 (3de60d5)

• Steps to reproduce:

  1. Open about:brave with kabob > Help > About Brave.
  2. Hover over the copy to clipboard button as shown in the screenshot below.

• Actual result:
  No tooltip is shown.

• Expected result:
  The tooltip Copy to clipboard should be shown.

• Will the steps above reproduce in a fresh profile? If not what other info can be added?
  Yes.

• Is this an issue in the currently released version?
  Yes, 0.14.1.

• Can this issue be consistently reproduced?
  Yes.

• Extra QA steps:

  1. Open about:brave with kabob > Help > About Brave.
  2. Hover over the copy to clipboard button as shown in the screenshot below.
  3. Make sure the tooltip Copy to clipboard tooltip is shown.

• Screenshot if needed:
  

• Any related issues:
  None.