DOC: add behavior change note for only considering fonts in registry

Author: tacaswell

doc/api/next_api_changes/behavior/24655-AK.rst

@@ -0,0 +1,14 @@
+On windows only fonts known to the registry will be discovered
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Previously, Matplotlib would recursively walk user and system font directories
+to discover fonts, however this lead to a number of undesirable behaviors
+including finding deleted fonts.  Now Matplotlib will only find fonts that are
+known to the Windows.
+
+This means that any user installed fonts must got through the Windows font
+installer rather than simply being copied to the correct folder.
+
+This only impacts the set of fonts Matplotlib will consider when using
+`matplotlib.font_manager.find_font`, directly pass the path to a font to use an
+arbitrary font (see :doc:`/gallery/text_labels_and_annotations/fonts_file`).