Release 2.1.1

[2.1.1] 2023-04-28

Version 2.1.1 release of Bilby

Bugfix release

Changes

• Fix the matched filter SNR phase for the multiband likelihood (!1253 (merged))
• Bugfix for Fisher matrix proposals in bilby_mcmc (!1251 (merged))
• Make the changes to the spline calibration backward compatible, 2.0.2 resume files can't be read with 2.1.0 (!1250 (merged))

This is a bugfix release. The most important change here is the fix to the Fisher matrix conditioning.

I've attempted to start a new system where we ask our reviewers (@simon-stevenson and @charlie.hoy) to sign off on releases so that we can jump into the IGWN environments quickly.

cc @gregory.ashton