Remove focus ring from focussed tab

Removed blue outline on focussed tab:
https://www.moneyadviceservice.org.uk/en/tools/pension-calculator/stewd?utf8=%E2%9C%93&display_frequency=yearly&dob_day=4&dob_month=9&dob_year=1968&gender=male&pot_1=0&pot_2=0&pot_3=0&pot_employee_contribution_currency=0&pot_employee_contribution_currency_frequency=yearly&pot_employee_contribution_datatype=currency&pot_employee_contribution_percentage=0&pot_employer_contribution_currency=0&pot_employer_contribution_currency_frequency=yearly&pot_employer_contribution_datatype=currency&pot_employer_contribution_percentage=0&salary=9288&salary_frequency=yearly&salary_range_salary=1545&salary_range_salary_frequency=monthly