Revise maturity dates for VSM and Code Analytics

The Maturity page showed Code Analytics and VSM as moving to the next maturity level at the end of this month (January). The categories.yml shows that this was based on a hiring plan that was not realized. We are operating at 50% of the projected hiring plan.

This MR pushes Code Analytics Viable maturity to the end of 2021 and changes the priority from Medium to Low because the priority for much of 2021 will be maturing the VSM and DevOps Reports categories. It also pushes the Viable maturity for DevOps Reports from January to mid year and increases the priority to High.