Bump knapsack_pro from 3.0.0 to 3.3.1

Bumps [knapsack_pro](https://github.com/KnapsackPro/knapsack_pro-ruby) from 3.0.0 to 3.3.1.
- [Release notes](https://github.com/KnapsackPro/knapsack_pro-ruby/releases)
- [Changelog](https://github.com/KnapsackPro/knapsack_pro-ruby/blob/master/CHANGELOG.md)
- [Commits](https://github.com/KnapsackPro/knapsack_pro-ruby/compare/v3.0.0...v3.3.1)

---
updated-dependencies:
- dependency-name: knapsack_pro
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile.lock

@@ -354,7 +354,7 @@ GEM
       activerecord
       kaminari-core (= 1.2.2)
     kaminari-core (1.2.2)
-    knapsack_pro (3.0.0)
+    knapsack_pro (3.3.1)
       rake
     kramdown (2.3.1)
       rexml
@@ -751,7 +751,7 @@ DEPENDENCIES
   jquery-rails (~> 4.4.0)
   jquery-ui-rails (~> 6.0.1)
   kaminari (~> 1.2.2)
-  knapsack_pro (~> 3.0.0)
+  knapsack_pro (~> 3.3.1)
   launchy (~> 2.5.0)
   letter_opener_web (~> 1.4.0)
   mdl (~> 0.11.0)