Release v0.2.1

It's 0.2.1 instead of 0.2.0 to work around build number resetting after we moved
into separate repo, this way new dev builds will become 0.2.2-dev{build} and so
will be higher than previously built dev builds that has 0.2.1-dev{higher-build-num}

odc/stac/_version.py

@@ -1,2 +1,2 @@
 """version information only."""
-__version__ = "0.2.0a9"
+__version__ = "0.2.1"