Replace env.deprecated_call() with pytest.deprecated_call() (#5893)

Since we already require pytest>=6 (see tests/requirements.txt), the
old compatibility function is obsolete and pytest.deprecated_call() can
be used directly.

Extracted from PR #5879

Co-authored-by: Michael Carlstrom <rmc@carlstrom.com>
Co-authored-by: gentlegiantJGC <gentlegiantJGC@users.noreply.github.com>

tests/env.py

@@ -4,8 +4,6 @@ import platform
 import sys
 import sysconfig
 
-import pytest
-
 ANDROID = sys.platform.startswith("android")
 LINUX = sys.platform.startswith("linux")
 MACOS = sys.platform.startswith("darwin")
@@ -29,19 +27,3 @@ TYPES_ARE_IMMORTAL = (
     or GRAALPY
     or (CPYTHON and PY_GIL_DISABLED and (3, 13) <= sys.version_info < (3, 14))
 )
-
-
-def deprecated_call():
-    """
-    pytest.deprecated_call() seems broken in pytest<3.9.x; concretely, it
-    doesn't work on CPython 3.8.0 with pytest==3.3.2 on Ubuntu 18.04 (#2922).
-
-    This is a narrowed reimplementation of the following PR :(
-    https://github.com/pytest-dev/pytest/pull/4104
-    """
-    # TODO: Remove this when testing requires pytest>=3.9.
-    pieces = pytest.__version__.split(".")
-    pytest_major_minor = (int(pieces[0]), int(pieces[1]))
-    if pytest_major_minor < (3, 9):
-        return pytest.warns((DeprecationWarning, PendingDeprecationWarning))
-    return pytest.deprecated_call()