Remove choice between MD TG 1.3 and TG 2.0

[DanielMartinPerezdeLeon]

As agreed during the 78th MIG-T meeting on 17 May 2024, after the deprecation of MD TG 1.3, the possibility to run tests for this TG version will be removed from the Validator in the release v.2024.3 planned for 15 September 2024 (see the release plan).

Hence, the choice between MD TG 1.3 and TG 2.0 will be removed, and by default when selecting Metadata as the resource type, only the tests deriving from TG 2.0 will be presented, i.e. the next question will be the one with a choice between Data sets and data set series, Network Service and Spatial Data Service.

Source code must also be revised to remove remaining options, CCs and IDs associated to MD TG 1.3.