Multisig: remove multisigs from cache for all networks when secret is removed

Fix an issue where multisigs related to a secret were removed from the cache only for the currently selected network when the secret was removed.

If you want to test the difference in behavior:

1. Add an implicit which comes with some multisigs on ghostnet
2. Switch to mainnet
3. Remove the implicit from umami
4. Switch back to Ghostnet: multisigs related to deleted account are present in the contract tab (or are not if you test the proposed patch)

Fixes #962 (closed)