REMOVE tessagon from build system and leave it only in tests.

Author: pv

pyproject.toml

@@ -1,5 +1,5 @@
 [build-system]
-requires = ["scikit-build-core >=0.10", "nanobind >=1.3.2", "tessagon"]
+requires = ["scikit-build-core >=0.10", "nanobind >=1.3.2"]
 build-backend = "scikit_build_core.build"
 
 [project]