clean up securityAlertProvider from signature controller

[blackdevelopa]

Explanation

Clean up securityAlertProvider SignatureController? Context

References

• Fixes #4102

Changelog

@metamask/signature-controller

• BREAKING: Removed securityProviderRequest property from SignatureController

Checklist

• [ ] I've updated the test suite for new or updated code as appropriate
• [ ] I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• [ ] I've highlighted breaking changes using the "BREAKING" category above as appropriate