Remove avg_cycle_analytics from usage ping

What does this MR do?

We're planning to replace the old implementation of value stream (cycle analytics) backend and during the refactor this class and its specs caused some troubles.

This MR removes the avg_cycle_analytics key from usage ping. The value stream calculation (cycle analytics) of the last N active project is not quite useful and as far as I know it's not used at all.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #271538 (closed)