v1 release should be anthenea but is athenea

[holtgrewe]

Describe the bug
We have named the branch etc. athenea but it should be anthenea with an n after the a.

To Reproduce
N/A

Expected behavior
Things should be named and labeled anthenea.

Screenshots
N/A

Additional context
N/A

[holtgrewe]

Root Cause Analysis
N/A

[holtgrewe]

Resolution Proposal
Rename the branch and change names in other places. As for file downloads, we can simply provide a symlink for athenea for a while.

Affected Components
VarFish Server

Affected Modules/Files

docs_manual/admin_install.rst
docs_manual/admin_upgrade.rst
docs_manual/developer_data_builds.rst
docs_manual/release_cycle.rst
HISTORY.rst

Required Architectural Changes
None

Resolution Sketch

• use search and replace to adjust documentation
• rename branch