[Format] Should there be a copy of adbc.h in the Arrow repository

[CurtHagenlocher]

Describe the bug, including details regarding any error messages, version, and platform.

The copy of adbc.h in the Arrow repository does not include ADBC 1.1 and later changes. Should there even be a copy here? If not, perhaps it ought to be removed. If so, it should be updated.

I tentatively think it should be removed.

Component(s)

Format

[kou]

@lidavidm What do you think about this?

BTW, we should backport #38953 to apache/arrow-adbc.

[lidavidm]

I'd rather remove the copy here since it's just going to get out of sync