Delete limitedmap as it is unused now

Summary:
Partial backport of core#19988:
https://github.com/bitcoin/bitcoin/pull/19988/commits/86f50ed10f66b5535f0162cf0026456a9e3f8963

Depends on D9552.

Test Plan:

ninja all check

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D9553