Convert Minor Schema Update GHA workflows to be manually dispatched

[nayib-jose-gloria]

1) https://github.com/chanzuckerberg/single-cell-curation/blob/main/.github/workflows/minor-schema-version-bump.yml 2) https://github.com/chanzuckerberg/single-cell-curation/blob/main/.github/workflows/trigger-schema-migration.yml

Update both these workflows to be manually dispatched via the Github UI, as major schema updates may also include changes to the files in the provided trigger paths and should have manual dispatches by engineers upon request from Lattice/Product.

[danieljhegeman]

@nayib-jose-gloria I'm a bit confused: title specifies Minor but the description specifies major

edit: ok the first one is minor updates, and the second one is major version updates.

and with

as major schema updates may also

the emphasis is on may also i.e. similar to minor version bump