SpiceUserManual.xml: small clean-ups

Remove some non-conventional/non-freesoftware editor-specific lines.

Remove trailing whitespaces

Get rid of DTD, which is too strict for docbook, see also:
http://docbook.org/tdg5/en/html/ch02.html

This get rids of the following warning/error:

I/O error : Attempt to load network entity
http://docbook.org/xml/5.0/dtd/docbook.dtd
/home/elmarco/src/spice/spice-master/docs/manual/SpiceUserManual.xml:4:
warning: failed to load external entity
"http://docbook.org/xml/5.0/dtd/docbook.dtd"
          "http://docbook.org/xml/5.0/dtd/docbook.dtd">
                                                       ^

0 files changed, 0 insertions, 0 deletions