Update tempest version required

I093be875910ef18deebe3e56b83c6992d1a307e5 introduced the
use of newer code from tempest that isn't available until
the 31.1.0 release.

Change-Id: Ibe2946fafd4d2b58d49b6c4040887346df1f9899
Related-Bug: #1968069
Signed-off-by: Goutham Pacha Ravi <gouthampravi@gmail.com>
1 file changed