spec: Fix formatting of example of memory port types. (#2368) (#2370)

8abf3085

 reordered the fields, but it
unintentionally placed a closing brace before the actual end of the
write port type. This moves the brace to the end of the port.

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
(cherry picked from commit b2cae19b

)

# Conflicts:
#	spec/spec.pdf

Co-authored-by: Richard Xia <rxia@sifive.com>