docs: remove non-breaking spaces from sedf_scheduler_mini-HOWTO.txt

docs: remove non-breaking spaces from sedf_scheduler_mini-HOWTO.txt

This document contains several 0xa0 characters (non-breaking spaces). These do
not display correctly in (some) terminals or when the document is rendered by (some)
browsers. Re-encode them as spaces.

I'm not confident that this change will make it through being encoded as a patch
and sent through email. Its effect can be replicated with:

	perl -i -p -e 's/\xa0/ /g' docs/misc/sedf_scheduler_mini-HOWTO.txt

[ I ran the rune rather than trying to apply the patch -iwj ]

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>