Replace the email icon with the external link icon on the census tract feedback button

[KameronKerger]

Describe the bug Now that census tract feedback is a SurveyMonkey survey and not an email, the icon on the button should be updated to be an external link icon and not the email icon.

To Reproduce Steps to reproduce the behavior:

1. Go to 'Explore the map'
2. Click on 'any census tract'
3. See error

Expected behavior External links should have the external link icon

Screenshots If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context Add any other context about the problem here.