fix(dev): Pin hatchling to 1.29.0 (#533)

About an hour ago, a new version of our build system, Hatchling
(1.30.0), was released.  This sets the metadata-version to 2.5.  But
that version is not supported by Twine, our PyPI upload system.

I haven't researched if there's a better option, but this should deal
with the immediate problem.  At the least, we should update Hatchling
once Twine is able to handle 2.5.

Author: jholveck

pyproject.toml

@@ -1,5 +1,5 @@
 [build-system]
-requires = ["hatchling"]
+requires = ["hatchling==1.29.0"]
 build-backend = "hatchling.build"
 
 [project]