Remove `#include <pybind11/type_caster_pyobject_ptr.h>` from absl_casters.h

While working on https://github.com/pybind/pybind11/pull/4674 I came to realize that this include is not needed here.

Note however that the pybind11/cast.h changes under https://github.com/pybind/pybind11/pull/4601 are still needed, therefore pybind11_abseil still requires current pybind11 master.

PiperOrigin-RevId: 533182724

WORKSPACE

@@ -33,6 +33,15 @@ http_archive(
   build_file = "@pybind11_bazel//:pybind11.BUILD",
   strip_prefix = "pybind11-master",
   urls = ["https://github.com/pybind/pybind11/archive/refs/heads/master.tar.gz"],
+  # For easy local testing with pybind11 releases:
+  #   * Comment out the 2 lines above.
+  #   * Uncomment and update the 3 lines below.
+  #   * To compute the sha256 string:
+  #       * Download the .tar.gz file (e.g. curl or wget).
+  #       * sha256sum v2.10.4.tar.gz
+  # strip_prefix = "pybind11-2.10.4",
+  # sha256 = "832e2f309c57da9c1e6d4542dedd34b24e4192ecb4d62f6f4866a737454c9970",
+  # urls = ["https://github.com/pybind/pybind11/archive/refs/tags/v2.10.4.tar.gz"],
 )
 
 load("@pybind11_bazel//:python_configure.bzl", "python_configure")

pybind11_abseil/absl_casters.h

@@ -33,7 +33,6 @@
 #include <pybind11/cast.h>
 #include <pybind11/pybind11.h>
 #include <pybind11/stl.h>
-#include <pybind11/type_caster_pyobject_ptr.h>
 
 // Must NOT appear before at least one pybind11 include.
 #include <datetime.h>  // Python datetime builtin.