Fully drop uom column from tally measurements table

After https://issues.redhat.com/browse/SWATCH-430 is released, we need to fully drop the uom column from the instance measurements.

The only thing to do is to uncomment this line: https://github.com/RedHatInsights/rhsm-subscriptions/blob/44dd2e7388334af898ab4b33d0c4f90739262b7d/src/main/resources/liquibase/changelog.xml#L129

Note: blocked by SWATCH-430 being in production.