ENH: Update pyproject.toml for ITK 5.4.2

In preparation for release.

Ensure that cmake is 3.16.3 or greater to
match v5.4.2 minimum requirements.

Set minimum python to 3.9

Increment version number.

Replace keyword of "ITK" with lowercase "itk"
in some instances to be consistent.

Author: hjmjohnson

pyproject.toml

@@ -47,7 +47,7 @@ Homepage = "https://github.com/InsightSoftwareConsortium/ITKMeshToPolyData"
 # The versions of CMake to allow. If CMake is not present on the system or does
 # not pass this specifier, it will be downloaded via PyPI if possible. An empty
 # string will disable this check.
-cmake.version = ">=3.16"
+cmake.version = ">=3.16.3"
 
 # A list of args to pass to CMake when configuring the project. Setting this in
 # config or envvar will override toml. See also ``cmake.define``.