MAINT: Remove use of label kwarg

[aburrell]

Description

After pysat 3.2.0 is the latest supported version of pysat, the label Instrument kwarg will no longer need to be supported.

Potential impact

• Is the feature related to an existing problem? Some support methods use the label kwarg, which has been deprecated
• How critical is this feature to your workflow? Important for maintanability
• How wide of an impact to you anticipate this enhancement having? Important for developers
• Would this break any existing functionality? No

Potential solution(s)

Identify places in the code where a pysat Instrument is called using labels and replace with meta_kwargs.

Alternatives

Continue to support kwargs of no-longer-supported pysat versions