Removes the ability to view server config files in TP as they are no longer reliable

[mitchell852]

What does this PR (Pull Request) do?

With the introduction of atstccfg, the contents of cache server config files as determined through the TO API are no longer reliable (as it really depends on the version of atstccfg running on the cache), therefore, this functionality is being removed from TP.

Users will still be able to see a list of config files applicable to a cache server but not its contents. To see the contents of a cache you will have to be on that cache and perform a command such as:

/opt/ort/atstccfg -s -n host-name \
        -P ... -U ... \
        -u "https://trafficops.domain.net/api/2.0/servers/{host-name}/configfiles/ats/remap.config"

• This PR fixes Viewing cache server config files in TP is broken (404) #4776

Which Traffic Control components are affected by this PR?

• Traffic Portal

What is the best way to verify this PR?

• Navigate to a cache server (edge or mid). i.e. https://tp.domain.com/#!/servers/29
• Select More -> View Config Files; verify that a list of config files is displayed
• Verify that viewing the contents of each config file is not an option.

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

• master
• 4.1.0 (RC1)

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)

[rawlinp]

Verified that TP shows the list of config files for a cache but no longer provides the ability to view/download individual files.