About dialog does not allow copying text to clipboard

[gulkily]

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

Describe the issue you encountered:
In the About dialog, the text can be selected, but is not copied to the clipboard when I press Cmd+C.

Expected behavior:
Selected text should be copied to the clipboard.

• Platform (Win7, 8, 10? macOS? Linux distro?): macOS
• Brave Version: 0.11.5
• Steps to reproduce:
  1. Open the About dialog (Brave menu > About Brave)
  2. Select some or all of the text in the dialog
  3. Press Cmd+C
  4. Open something with a text field
  5. Press Cmd+V

Expected: Text is copied to the clipboard in step 3, pasted in step 5

Actual: Text is not copied to the clipboard.

[bbondy]

duping to #463