Add stage to deprecated jobs

What does this MR do and why?

CI configs without a default stage break because 2 deprecated Dependency Scanning jobs are missing a stage definition.

This is a result of this MR: !87563 (comment 947625584)

Here's an example: gitlab-org/security-products/tests/ruby-bundler!1294 (a2801865)

Tests

• Error with 15.0 DS config: https://gitlab.com/gitlab-org/security-products/tests/ruby-bundler/-/pipelines/540225952
• Fix including the DS config from this MR: https://gitlab.com/gitlab-org/security-products/tests/ruby-bundler/-/pipelines/540227216

These are strongly recommended to assist reviewers and reduce the time to merge your change.