Backport PR matplotlib#24301: Restore get_renderer function in deprec…

…ated tight_layout

lib/matplotlib/tight_layout.py

@@ -1,3 +1,13 @@
 from matplotlib._tight_layout import *  # noqa: F401, F403
 from matplotlib import _api
 _api.warn_deprecated("3.6", name=__name__, obj_type="module")
+
+
+@_api.deprecated("3.6", alternative="figure.canvas.get_renderer()")
+def get_renderer(fig):
+    canvas = fig.canvas
+    if canvas and hasattr(canvas, "get_renderer"):
+        return canvas.get_renderer()
+    else:
+        from . import backend_bases
+        return backend_bases._get_renderer(fig)