update constraint for mistral-lib to new release 3.2.0

meta: version: 3.2.0
meta: team: mistral
meta: diff-start: -
meta: series: epoxy
meta: branch: master
meta: release-type: release
meta: pypi: yes
meta: first: no
meta: release:Author: Arnaud Morin <arnaud.morin@gmail.com>
meta: release:Commit: Arnaud Morin <arnaud.morin@gmail.com>
meta: release:Change-Id: I4592aac7acf011873c8d9213b7475d1505a39369
meta: release:Code-Review+1: Axel Vanzaghi <avanzaghi.osf@axellink.fr>
meta: release:Code-Review+2: Elod Illes <elod.illes@est.tech>
meta: release:Code-Review+2: Dr. Jens Harbott <frickler@offenerstapel.de>
meta: release:Code-Review+1: Hervé Beraud <herveberaud.pro@gmail.com>
meta: release:Workflow+1: Elod Illes <elod.illes@est.tech>
Change-Id: I1f2d5a2bb0758c6b0c109588532d6d4a18da0d06

Author: OpenStack Proposal Bot

upper-constraints.txt

@@ -292,7 +292,7 @@ threadpoolctl===3.5.0
 os-ken===2.11.2
 ujson===5.10.0
 selenium===3.141.0
-mistral-lib===3.1.0
+mistral-lib===3.2.0
 dogtag-pki===11.2.1
 XStatic-Angular-UUID===0.0.4.0
 purestorage===1.19.0