qemu-doc: Remove the "CPU emulation" part of the "Implementation notes"

qemu-doc: Remove the "CPU emulation" part of the "Implementation notes"

The "CPU emulation" part of the "Implementation notes" in
qemu-tech.texi looks like it is documenting what features of various
CPUs we do or don't emulate.  However:
 * it covers only six of our 21 guest architectures
 * the last time anybody updated it for actual content was in
   2011/2012 for Xtensa; the content for the other five
   architectures is even older, being from 2008 or before!

What we have is out of date, misleading and incomplete.
Just delete this part of the document rather than trying to
convert it to rST.

(It would be nice eventually to have documentation of the
scope and limitations of our emulation; but we will want to
separate out the generic "system emulation" information from
the parts that are specific to linux-user anyway, as they will
be in different manuals.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 20200228153619.9906-10-peter.maydell@linaro.org
Message-id: 20200226113034.6741-10-pbonzini@redhat.com
Message-Id: <20200225154121.21116-3-peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>