Unified signing keys across Mux Data and Video products

Signing keys are used to sign JSON Web Tokens (JWTs) to authenticate and enumerate certain requests to the Mux APIs.  Creating separate signing keys for Video and Data URLs is no longer required and the signing keys page has been updated to remove the notion of separate Video and Data signing keys. Any signing keys customers have created in the past will continue to work. Customers will need to use a System access token to create signing keys going forward. See our documentation for signing JWTs and for our signing key API for more details.