remove hack that sets 0-width to glyph.xMax

this messes up horizontal positioning of glyphs with zero advance width, was added to prevent clipping of bitmap glyphs exceeding their viewbox (#402). The latter issue will be dealt with separately.

src/nanoemoji/colr_to_svg.py

@@ -312,10 +312,6 @@ def glyph_region(ttfont: ttLib.TTFont, glyph_name: str) -> Rect:
 
     map_font_space_to_viewbox handles font +y goes up => svg +y goes down."""
     width = ttfont["hmtx"][glyph_name][0]
-    if width == 0:
-        glyph = ttfont["glyf"][glyph_name]
-        if hasattr(glyph, "xMax"):  # empty glyphs have no bbox attributes
-            width = glyph.xMax
     return Rect(
         0,
         -ttfont["OS/2"].sTypoAscender,