Groebner v0.6.1

Diff since v0.6.0

Merged pull requests:

• CompatHelper: bump compat for AbstractAlgebra to 0.35, (keep existing compat) (#102) (@github-actions[bot])
• CompatHelper: bump compat for Nemo to 0.39, (keep existing compat) (#103) (@github-actions[bot])
• Create Downgrade.yml (#104) (@sumiya11)