Remove commit_frequency_ms from MagicBlock Protocol v2

Goal

Remove commit_frequency_ms from the MagicBlock Protocol v2 program's instruction arguments and delegation state as part of #132.

Why

commit_frequency_ms is not used by MBV or any other project. Users who want regular commits should use the Hydra cranker. Remove the unused field from MagicBlock Protocol v2 rather than retain a setting that has no effect.

Scope

• Remove the field from v2 delegation arguments and account layouts, including delegation-with-actions and other delegation paths.
• Remove corresponding initialization and handling; update the v2 API, IDL, instruction builders, fixtures, and documentation to match.
• Keep v1 interfaces and layouts unchanged; make the v2 layout change explicit so consumers do not interpret v1 data as v2.
• Verify that v2 delegation works without supplying a commit frequency and that v2 artifacts contain no references to the removed field.

Introducing a replacement scheduling mechanism or changing unrelated delegation behavior is out of scope.