[eCash dev libraries] [p12 ecash-ops] Typo fix in ecash-minimaldata

Summary:
T2847

Depends on D12868

Patch confusing typo in README for ecash-minimaldata

Test Plan: Confirm that package name matches directory name matches README references

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Subscribers: emack

Differential Revision: https://reviews.bitcoinabc.org/D12869