Fix example_branch_operator failing in python 3.12 (#39783)

Recently, this dag started failing due to python 3.12 removal of some
deprecated symbols. The fix here was moving to a higher version of
numpy as the old version uses pinned setuptools

(cherry picked from commit 61e9070)

airflow/example_dags/example_branch_operator.py

@@ -141,7 +141,7 @@ def branch_with_venv(choices):
 
         branching_venv = BranchPythonVirtualenvOperator(
             task_id="branching_venv",
-            requirements=["numpy~=1.24.4"],
+            requirements=["numpy~=1.26.0"],
             venv_cache_path=VENV_CACHE_PATH,
             python_callable=branch_with_venv,
             op_args=[options],
@@ -162,7 +162,7 @@ def hello_world_with_venv():
         for option in options:
             t = PythonVirtualenvOperator(
                 task_id=f"venv_{option}",
-                requirements=["numpy~=1.24.4"],
+                requirements=["numpy~=1.26.0"],
                 venv_cache_path=VENV_CACHE_PATH,
                 python_callable=hello_world_with_venv,
             )