Address deprecated DataFrame concatenation in data_utils

[hernandezc1]

In testing the changes made to PR #216, the following warning appeared in the tag cloud function logs:

/layers/google.python.pip/pip/lib/python3.12/site-packages/broker_utils/data_utils.py:319: FutureWarning: The behavior of DataFrame concatenation with empty or all-NA entries is deprecated. In a future version, this will no longer exclude empty or all-NA columns when determining the result dtypes. To retain the old behavior, exclude the relevant entries before the concat operation.

We will need to address the deprecation of DataFrame concatenation with empty or all-NA entries.

[troyraen]

Can you post a Google Console link to the error so we can see the full traceback?