Remove dast_ods_browser_based_scanner feature flag

What does this MR do and why?

Removes the feature flag dast_ods_browser_based_scanner and its frontend counterpart dastOdsBrowserBasedScanner since the feature has been rolled out on production fully in 17.0

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

How to set up and validate locally

Setup an on-demand scan on your GDK https://docs.gitlab.com/ee/user/application_security/dast/on-demand_scan.html

Related to #430499