Traffic Portal tests in CiaB: Pin ChromeDriver to version of Chrome that we installed

[zrhoffman]

What does this PR (Pull Request) do?

• This PR is not related to any Issue

When the ChromeDriver version that webdriver-mananger installs is newer than the version of Chrome that is installed, the traffic_portal_integration_test CDN-in-a-Box container fails with

portal-integration-test_1  | [06:09:06] E/launcher - SessionNotCreatedError: session not created: This version of ChromeDriver only supports Chrome version 85

Which Traffic Control components are affected by this PR?

• CDN in a Box

What is the best way to verify this PR?

Run TP tests in CDN-in-a-Box and verify they succeed.

docker-compose up -d trafficportal trafficops trafficvault && \
docker-compose -f docker-compose.yml -f docker-compose.traffic-portal-test.yml up --build portal-integration-test

If this is a bug fix, what versions of Traffic Control are affected?

• master (cc3e677)
• 4.1.0

The following criteria are ALL met by this PR

• This PR fixes tests
• Bugfix, no documentation necessary
• An update to CHANGELOG.md is not necessary
• This PR includes any and all required license headers
• This PR does not include a database migration
• This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)