Install libgit2-dev in docker build

[sushantmimani]

To help us get this pull request reviewed and merged quickly, please be sure to include the following items:

• Tests (if applicable)
• Documentation (if applicable)
• Changelog entry
• A full explanation here in the PR description of the work done

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Tests
• Other

Backward Compatibility

Is this change backward compatible with the most recently released version? Does it introduce changes which might change the user experience in any way? Does it alter the API in any way?

• Yes (backward compatible)
• No (breaking changes)

What's new?

• Install libigt2-dev while building the docker image

[tarkatronic]

I'd say the version bump isn't necessarily... necessary. Since we're hopefully doing an RC within a day or two. But that said, no harm in another alpha release!