Miscellaneous doc fixes

[taharallouche]

I fixed two spots in the doc:

• The Mace aggregator doc had some broken mathematical symbols. (missing $ and raw strings).
• The Consistency metric's docstring refers to a Dawid-Skene model whereas the aggregator is actually an attribute of the class and can be any BaseClassificationAggregator.

If the changes are OK, would you like me to squash the commits ?

Checklist

• I have read the CONTRIBUTING document
• I hereby agree to the terms of either individual CLA available at: https://toloka.ai/legal/cla_individual or corporate CLA available at: https://toloka.ai/legal/cla_corporate, whichever is applicable to me, as it pertains to direct contributions to crowd-kit only
• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed