Use `cairo_show_text_glyphs`

[chearon]

I forgot to do this in #2602

node-canvas/src/CanvasRenderingContext2d.cc

Lines 2546 to 2547 in 8ccddbe

	// TODO: use cairo_show_text_glyphs !
	cairo_show_glyphs(context(), glyphs, numGlyphs);

This is a harder API to use, but I need to do it so that v4 doesn't break text being embedded in PDFs.