Cancel previously-announced change to MobSF

What does this MR do?

Update the previously-announced MobSF change notice to state that the change is no longer happening.

Per @jamesliu-gitlab in gitlab-org/security-products/analyzers/mobsf!73 (comment 1387767716):

The deprecation warnings no longer apply due to this change -- we now support proper scanning of multimodule Android projects and more.

Choice: delete the notice entirely, or update the contents?

I chose to update the contents in case the breaking change notice had been linked to elsewhere. Someone might have a link to https://docs.gitlab.com/ee/update/deprecations.html#changing-mobsf-based-sast-analyzer-behavior-in-multi-module-android-projects. If they did and we totally removed it, they'd just land at the top of the Deprecations page with no information about the deprecation being cancelled.

Related issues

#408396 (closed)

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