Bump project file format revision

[vkbo]

Summary:

The file format revision number was not bumped in the 2.3 release. This isn't a big issue, it's mostly for the sake of third party file converters. But adding the Templates class should have bumped the file format.

Related Issue(s):

Reviewer's Checklist:

• The header of all files contain a reference to the repository license
• The overall test coverage is increased or remains the same as before
• All tests are passing
• All flake8 checks are passing and the style guide is followed
• Documentation (as docstrings) is complete and understandable
• Only files that have been actively changed are committed