Unpin pandas and upgrade to latest version

Pandas was previously pinned to version < 1.2 due due to the way that it
parses large integer values from Excel. Those values are transformed incorrectly
by openpyxl into a floating point number before casting into a string, changing
their value. This was primarily impacting ingestion of barcode fields.

With the transition away from ingesting aliquoting sheets and incident reports from
Excel (replaced by API endpoints), this is no longer an issue.

Author: davereinhart