Update upgrade instructions for 2.5.0 release

- Bump up minimum OpenSRF to 2.2.1
- Replace all 2.5-beta1 markers (and few stray 2.4 markers) with 2.5.0

Signed-off-by: Dan Wells <dbw2@calvin.edu>
Update OpenSRF minimum version in install docs

Evergreen now requires OpenSRF 2.2.1 or later, so it makes sense to be
clear about it.

Signed-off-by: Dan Wells <dbw2@calvin.edu>