Merge pull request matplotlib#21602 from meeseeksmachine/auto-backport-of-pr-21586-on-v3.5.x

Backport PR matplotlib#21586 on branch v3.5.x (Defer enforcement of hatch validation)

Author: tacaswell

lib/matplotlib/hatch.py

@@ -188,6 +188,7 @@ def _validate_hatch_pattern(hatch):
             invalids = ''.join(sorted(invalids))
             _api.warn_deprecated(
                 '3.4',
+                removal='3.7',  # one release after custom hatches (#20690)
                 message=f'hatch must consist of a string of "{valid}" or '
                         'None, but found the following invalid values '
                         f'"{invalids}". Passing invalid values is deprecated '