Fix version of jupyter-packaging in pyproject.toml

The specifier `~=0.9` is equivalent to `>= 0.9, == 0.*` so there is no need to specify `<2`.
jupyter · kevin-bates · Jul 13, 2021 · Jun 30, 2021 · Jun 30, 2021 · 4f397ab9d6d082e0c8b7b6562f3aaf3e06e35085
commit 4f397ab9d6d082e0c8b7b6562f3aaf3e06e35085
diff --git a/pyproject.toml b/pyproject.toml
@@ -1,5 +1,5 @@
 [build-system]
-requires=["jupyter_packaging~=0.9,<2"]
+requires=["jupyter_packaging~=0.9"]
 build-backend = "setuptools.build_meta"
 
 [tool.check-manifest]