Update Pixi toml version for 5.12 release

[koettert]

Update knime-python-versions = 5.12.0 , knime-extension-bundling = 5.12.0 and knime-extension = 5.12.00 in the https://github.com/spatial-data-lab/knime-geospatial-extension/blob/main/knime_extension/pixi.toml

Relates to #430