Regenerate multiline reference images + fix test_render_multiline spacing

The descender-aware line spacing change (A→Aj in getbbox) affects all
multiline text rendering output. This updates:

Reference images (16 files):
- multiline_text{,_center,_right,_justify,_justify_anchor}.png
- multiline_text_spacing.png
- test_anchor_multiline_{anchor}_{align}.png (11 files)

Test fix:
- test_render_multiline: use getbbox('Aj') to match new line spacing

All 212 tests in test_imagefont.py pass.

Author: armorbreak001