Remove planner banner spec, as banner has expired

What does this MR do and why?

Removes spec as banner is expired https://gitlab.com/gitlab-org/gitlab/blob/be6b3b147b2c57b2e5f6f416a962ccf8d2c964f5/app/assets/javascripts/planner_role_banner/index.js#L12-12

Resolves #549650 (closed)

master broken incident gitlab-org/quality/engineering-productivity/master-broken-incidents#13918 (closed)

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