docs: show nogil in most examples (#5770)

Created using [mini-swe-agent](https://mini-swe-agent.com) and the propmt:

I'd like to find usages of PYBIND11_MODULE in the docs folder and add py::mod_gil_not_used() as a third argument if there ar
e only two arguments. These are examples, and it's really a good idea to always include that now.

I removed a few of the changes.

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

docs/advanced/cast/custom.rst

@@ -108,7 +108,7 @@ type is explicitly allowed.
     } // namespace pybind11
 
     // Bind the negate function
-    PYBIND11_MODULE(docs_advanced_cast_custom, m) { m.def("negate", user_space::negate); }
+    PYBIND11_MODULE(docs_advanced_cast_custom, m, py::mod_gil_not_used()) { m.def("negate", user_space::negate); }
 
 .. note::
 

docs/advanced/cast/functional.rst

@@ -56,7 +56,7 @@ trivial to generate binding code for all of these functions.
 
     #include <pybind11/functional.h>
 
-    PYBIND11_MODULE(example, m) {
+    PYBIND11_MODULE(example, m, py::mod_gil_not_used()) {
         m.def("func_arg", &func_arg);
         m.def("func_ret", &func_ret);
         m.def("func_cpp", &func_cpp);

docs/advanced/classes.rst

@@ -45,7 +45,7 @@ Normally, the binding code for these classes would look as follows:
 
 .. code-block:: cpp
 
-    PYBIND11_MODULE(example, m) {
+    PYBIND11_MODULE(example, m, py::mod_gil_not_used()) {
         py::class_<Animal>(m, "Animal")
             .def("go", &Animal::go);
 
@@ -112,7 +112,7 @@ The binding code also needs a few minor adaptations (highlighted):
 .. code-block:: cpp
     :emphasize-lines: 2,3
 
-    PYBIND11_MODULE(example, m) {
+    PYBIND11_MODULE(example, m, py::mod_gil_not_used()) {
         py::class_<Animal, PyAnimal /* <--- trampoline */, py::smart_holder>(m, "Animal")
             .def(py::init<>())
             .def("go", &Animal::go);
@@ -774,7 +774,7 @@ to Python.
 
     #include <pybind11/operators.h>
 
-    PYBIND11_MODULE(example, m) {
+    PYBIND11_MODULE(example, m, py::mod_gil_not_used()) {
         py::class_<Vector2>(m, "Vector2")
             .def(py::init<float, float>())
             .def(py::self + py::self)

docs/advanced/pycpp/numpy.rst

@@ -217,7 +217,7 @@ expects the type followed by field names:
     };
 
     // ...
-    PYBIND11_MODULE(test, m) {
+    PYBIND11_MODULE(test, m, py::mod_gil_not_used()) {
         // ...
 
         PYBIND11_NUMPY_DTYPE(A, x, y);
@@ -351,7 +351,7 @@ simply using ``vectorize``).
         return result;
     }
 
-    PYBIND11_MODULE(test, m) {
+    PYBIND11_MODULE(test, m, py::mod_gil_not_used()) {
         m.def("add_arrays", &add_arrays, "Add two NumPy arrays");
     }