Remove unused zones for tts.gsa.gov, calc.gsa.gov, discovery.gsa.gov, and gsaforecast.gsa.gov

[pauldoomgov]

• tts.gsa.gov was prepared but not delegated. It is fully served by the GSA.gov nameservers.
• calc.gsa.gov was prepared but not delegated. It is fully served by the GSA.gov nameservers.
• discovery.gsa.gov was prepared but not delegated. It is fully served by the GSA.gov nameservers.
• gsaforecast.gsa.gov was delegated to the wrong AWS Route53 nameservers and appears completely unused.

Note that GSA.gov is a DNSSEC enabled zone. While non-DNSSEC subdomains are technically allowed, it is suggested that any future delegations under gsa.gov are DNSSEC enabled.

This PR removes the unused zones and leaves a placeholder for tts.gsa.gov to help our future selves.

[pauldoomgov]

Some evidence to go with this PR:

$ host -t ns calc.gsa.gov
calc.gsa.gov is an alias for nsp-acqit-m3.net.helix.gsa.gov.

$ host -t ns discovery.gsa.gov
discovery.gsa.gov is an alias for buy.gsa.gov.
buy.gsa.gov is an alias for nsp-acqit-m3.net.helix.gsa.gov.

# The Route53 nameservers for gsaforecast.gsa.gov are:
# discovery_gsa_gov_ns = tolist([
#   "ns-1322.awsdns-37.org",
#   "ns-181.awsdns-22.com",
#   "ns-1992.awsdns-57.co.uk",
#   "ns-538.awsdns-03.net",
# ])
#
# Which does NOT match what is defined in the GSA.gov zone:
$ host -t ns gsaforecast.gsa.gov
gsaforecast.gsa.gov name server ns-848.awsdns-42.net.
gsaforecast.gsa.gov name server ns-229.awsdns-28.com.
gsaforecast.gsa.gov name server ns-1960.awsdns-53.co.uk.
gsaforecast.gsa.gov name server ns-1468.awsdns-55.org.

$ host -t a gsaforecast.gsa.gov
gsaforecast.gsa.gov has no A record