Ignore get_settlement_model obsolete overload mypy warning

[JosueNina]

Description

The stubs expose an obsolete GetSettlementModel(Security, AccountType) overload, which causes mypy to flag overrides that only declare the current single argument signature. Added it to the ignore list in run_syntax_check.py

Motivation and Context

N/A

Requires Documentation Change

N/A

How Has This Been Tested?

It was tested by running the script locally

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Refactor (non-breaking change which improves implementation)
• Performance (non-breaking change which improves performance. Please add associated performance test and results)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Non-functional change (xml comments/documentation/etc)

Checklist:

• My code follows the code style of this project.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• My branch follows the naming convention bug-<issue#>-<description> or feature-<issue#>-<description>