fix: use setuptools.build_meta as build backend

setuptools.backends.legacy:build does not exist in setuptools versions
shipped with Python 3.10 CI environments. setuptools.build_meta is the
correct PEP 517 entry point and has been stable since setuptools 42.

Author: srikrishna3118

pyproject.toml

@@ -1,6 +1,6 @@
 [build-system]
-requires = ["setuptools>=68", "wheel"]
-build-backend = "setuptools.backends.legacy:build"
+requires = ["setuptools>=42", "wheel"]
+build-backend = "setuptools.build_meta"
 
 [project]
 name = "cornet-framework"