Remove "Modes" trait from SECURITYSYSTEM device

[alexismdr]

Description

"Modes" is neither a required nor a recommended trait for a SECURITYSYSTEM device. Different Arm Levels are handled by ArmDisarm trait. Removed it.

Suggested changelog entry

Removed useless "Modes" trait from SECURITYSYSTEM device.

Related issues/external references

https://developers.home.google.com/cloud-to-cloud/guides/securitysystem

Types of changes

• Bug fix (non-breaking change which fixes)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
  • This change is only breaking for integrators, not for external standards or end-users.
• Documentation improvement

PR checklist

• I have checked there is no other PR open for the same change.
• I have read the Contribution Guidelines.
• I grant the project the right to include and distribute the code under the GNU.
• I have added tests to cover my changes.
• I have verified that the code complies with the projects coding standards.
• [Required for new sniffs] I have added MD documentation for the sniff.