chore: update versions of forum and grove plugin

Description

Updates the versions for the forum plugin and tutor-contrib-grove.

For the tutor-forum opencraft-release/nutmeg.2 contains the following PRs:

• https://github.com/open-craft/tutor-forum/pull/2
• https://github.com/open-craft/tutor-forum/pull/1

And the changes from kaustav/bump_ruby_version

0.5.0 of tutor-contrib-grove has not yet been release. But it will, pending this MR

Testing instructions

These changes can be tested as part of tutor-contrib-grove!43 (merged)