Update acisops/backstop_history to v3.2.1

[javierggt]

New variations of SI modes, and their associated RTS files, for Long Term ECS
measurements were created to provide a more flexible chip selection.
Backstop History was updated to incorporate these new RTS files in future
history assemblies.

Includes the following merges:

• PR #25: Incorporation of new RTS files for new Long Term ECS SI modes
• PR #24: New ECS RTS file, New method added, SCS-107 bug fixed
• PR #23: Remove unnecessary and incorrectly applied round off
• PR #22: Now processes a full continuity (science + vehicle commands) load as …
• PR #21: Update to the PR 20 prior to installation
• PR #20: Update for SCS-106 change and new power commands
• PR #19: Run on filesystems which are not case-sensitive
• PR #18: Replace Chandra.Time with cxotime
• PR #17: Modifications to Baskstop History to accommodate data structure change…
• PR #13: Changes to accomodate NLET events in normal, too and maneuver only loads
• PR #9: SHINY: migrate from Chandra.cmd_states / Ska.ParseCM to kadi
• PR #11: Shiny workflow update
• PR #10: Shiny workflow update
• PR #8: Setting up automated builds
• PR #7: Remove version from setup.py
• PR #6: Code changes needed for SCM versioning