Bump decidim to 0.31.0 (#155)

* bump decidim to 0.31.0

* Supplemental

Author: alecslupu

Gemfile

@@ -5,7 +5,7 @@ source "https://rubygems.org"
 ruby RUBY_VERSION
 
 #DECIDIM_VERSION = { github: "decidim/decidim", branch: "fix/user-groups", ref: "0a8f1218f6" }
-DECIDIM_VERSION = "0.31.0.rc2"
+DECIDIM_VERSION = "0.31.0"
 
 gem "decidim", DECIDIM_VERSION
 gem "decidim-core", DECIDIM_VERSION