Internal issue 3123 - IcToggleButtonGroup with margin styling creates border effect

When adding an X margin to a toggle group an increased border on the side of the margin appears within the button closest to the margin when it is toggled and then unfocused.

See [Stackblitz](https://stackblitz.com/edit/3sca81cc-2yc44zq2?file=src%2Fapp.tsx)

Reproduce the issue in the linked Stackblitz example and inspect the IcToggleButtonGroup styling involved when an X margin is applied. Verify the focused, toggled, and unfocused states near the margin. Done means the increased border effect no longer appears inside the button while the toggle group retains its intended styling.

Written by the indexing model from the issue text.