continue portal-term scrubbing from nmdc-schema

[turbomam]

following @mslarae13's PR

• Add slot to capture long read sequencing DNA extraction method #2662

continue deleting src/schema/portal_* files that only contain slots of interest to the submission portal, and those slot definitions have been moved to the submission portal

if we end up with some src/schema/portal_* files that only contain a very small number of slots, those could be consolidated into some other appropriate schema YAML file

[mslarae13]

https://github.com/microbiomedata/nmdc-schema/blob/main/src/schema/portal_sample_id.yaml
https://github.com/microbiomedata/nmdc-schema/blob/main/src/schema/portal_enums.yaml