build: Add support for NumPy 2.0 wheels

* Update lower bound on build-system pybind11 to v2.12.0 to add support for
  compiling for NumPy 2.0.
   - c.f. https://github.com/pybind/pybind11/releases/tag/v2.12.0
* Remove pybind11 submodule to use build-system instead.

fixup

.gitmodules

@@ -1,9 +1,6 @@
 [submodule "fastjet"]
 	path = fastjet-core
 	url = https://gitlab.com/fastjet/fastjet.git
-[submodule "pybind11"]
-	path = pybind11
-	url = https://github.com/pybind/pybind11.git
 [submodule "fastjet-contrib"]
 	path = fastjet-contrib
 	url = https://github.com/cms-externals/fastjet-contrib.git

MANIFEST.in

@@ -2,7 +2,6 @@ graft src
 graft tests
 graft fastjet-core
 graft fastjet-contrib
-graft pybind11
 global-exclude .git .gitmodules
 include LICENSE README.md pyproject.toml setup.py setup.cfg patch_clustersequence.txt
 exclude .cirrus.yml

pyproject.toml

@@ -2,7 +2,7 @@
 requires = [
     "setuptools>=42",
     "setuptools_scm[toml]>=3.4",
-    "pybind11>=2.6.1",
+    "pybind11>=2.12.0",
 ]
 build-backend = "setuptools.build_meta"