Proto/test: fix activity update in the model

Based on !12912 (merged)

What

The cycle of application computed for staking operation is incorrect for operations included in the last block of a cycle. We used the cycle of the predecessor block. This MR fix that.

Why

Cause the model was inaccurate

How

just take next cycle when predecessor is at the end of a cycle.

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR