Revert "[NWD] Further EPPlus fixes & improvements."

This reverts commit d0678ed0e8a7acc31363e9d08dc7d3899a8f2177.

Reason for revert: Workflow templates for xlsx files modify styling options in some cases.

Change-Id: Ief762b59af79be9071ff89753550b37c0da6bcbd
Reviewed-on: https://gnocchi-internal-review.git.corp.google.com/c/third_party/epplus/+/207762
Reviewed-by: Hughes Hilton <hugheshilton@google.com>