Minor edit on fo:bidi-override constraint

Editors:

The content model constraint for fo:bidi-override has a small error:

"An fo:bidi-override that is a descendant of an fo:leader or of 
[an-->the] fo:inline child of an fo:footnote may not have block-level 
children, unless it has a nearer ancestor that is an fo:inline-container."

Switch from "an fo:inline child" to "the fo:inline child", as shown 
above, because an fo:footnote has only one fo:inline child.

This will make the text similar to what is already there for fo:inline's 
constraint:  "An fo:inline that is a descendant of an fo:leader or of 
the fo:inline child of an fo:footnote may not have block-level children, 
unless it has a nearer ancestor that is an fo:inline-container."

Thanks,
Glen