Removed difficulty hack in monero_rx

[StriderDM]

Description

Removes the check that determines how difficulty is calculated for monero blocks based on block height.

Motivation and Context

Necessary for testnet reset

How Has This Been Tested?

cargo test --all --all-features

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Feature refactor (No new feature or functional changes, but performance or technical debt improvements)
• New Tests
• Documentation

Checklist:

• I'm merging against the development branch.
• I ran cargo-fmt --all before pushing.
• I ran cargo test successfully before submitting my PR.
• I have squashed my commits into a single commit.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.