TP removes unused configurable ds field descriptions

[mitchell852]

What does this PR (Pull Request) do?

When the delivery service (HTTP*, DNS*, Steering* and any_map) forms were enhanced to have better field tooltips, these configurable field descriptions were abandoned but never removed. This PR removes them.

• This PR is not related to any Issue

Which Traffic Control components are affected by this PR?

• Traffic Portal

What is the best way to verify this PR?

Start up TP and run the UI tests.

• new UI tests would not be necessary for this. the existing tests will verify that functionality has not changed in the UI as a result of this change.
• the configurability of ds field names/descriptions in TP was never documented so no need to remove any documentation.

The following criteria are ALL met by this PR

• This PR includes tests OR I have explained why tests are unnecessary
• This PR includes documentation OR I have explained why documentation is unnecessary
• This PR includes an update to CHANGELOG.md OR such an update is not necessary
• This PR includes any and all required license headers
• This PR ensures that database migration sequence is correct OR 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)

[asfgit]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/trafficcontrol-PR/3773/
Test PASSed.

[ocket8888]

UI tests pass, help text popups still work.