Remove redundant condition `usage_ping_feature?`

What does this MR do and why?

• Related to [Feature flag] Rollout of `feature_available_ch... (#422614 - closed) (closing some remaining follow-up)

Remove redundant condition usage_ping_feature? inside the namespace and project level feature check.

Usage Ping feature check has been moved inside License.feature_available? and the namespace and project level feature checks are now getting it for free.

The MR contains removals of spec examples because we are now testing internal implementation details of License.feature_available?. We have good test coverage for all the combinations when Registration (Usage Ping) features are available or not: https://gitlab.com/gitlab-org/gitlab/-/blob/cb89bd98ff1ac0dd898aee92e65c7479b5f9883e/ee/spec/models/license_spec.rb#L1061-1129.

At a higher level of abstraction we only need to test 2 scenarios:

• Feature exists when stub_licensed_features(the_feature_name: true)
• Feature does not exist when stub_licensed_features(the_feature_name: false)

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.