Fixing pandas/tests/indexes/multi/test_analytics.py to utilize python…
Modified reflect python3 format strings on pandas/tests/indexes/multi/test_analytics.py.  I ran the test and it passed like before.  ref [#29886](https://github.com/pandas-dev/pandas/issues/29886) and [#29547](https://github.com/pandas-dev/pandas/issues/29547).
>Should fix [#29886](https://github.com/pandas-dev/pandas/issues/29886) and [#29547](https://github.com/pandas-dev/pandas/issues/29547).

@AncientRickles can you please replace the word ```fix``` with the word ```ref```?

Just so it wouldn't close the issue. thanks @AncientRickles 