Remove otype-precision specific setbounds proposal

This assumed the architecture where otypes steal some bounds precision.
It's possible the idea should live on, but I couldn't find where we
talked about sealing stealing otype bits, and this paragraph says false
things about the architecture as it stands.

chap-architecture.tex

@@ -3173,12 +3173,6 @@ \section{Potential Future Changes to the CHERI Architecture}
   represents, and the caller might want to restrict these permissions before
   passing the sealed capability to another subsystem.
 
-\item
-  Provide a variant of \insnref{CSetBounds} that sets imprecise bounds
-  suitable for sealing with \insnref{CSeal}. In the 128-bit
-  representation, the bounds of sealed capabilities have stronger alignment
-  requirements than for unsealed capabilities.
-
 \item
   Add instructions for copying non-capability data from a capability register
   into a general-purpose integer register. A use case is when a function is called