chore: remove keyring-api dependency from transaction controller

Explanation

Remove dependency on @metamask/keyring-api from @metamask/transaction-controller as it was only used for types in unit tests.

[x] I've updated the test suite for new or updated code as appropriate
[x] I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
[x] I've highlighted breaking changes using the "BREAKING" category above as appropriate
[x] I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes