Update pricing / feature comparison titles

Why is this change being made?

This is a proposal to give users greater clarity when navigating to the feature comparison pages. If a user navigates from https://about.gitlab.com/pricing/ or https://customers.gitlab.com/plans to either https://about.gitlab.com/pricing/self-managed/feature-comparison/ or https://about.gitlab.com/pricing/gitlab-com/feature-comparison/ the title does not indicate whether the features and corresponding plans relate to GitLab.com or Self-Managed instances.

Before	After

Does this MR meet the acceptance criteria?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what

cc @mkarampalas @jstava @darawarde @fulfillment-group