Update puma from 4.3.2 to 4.3.3

Fixes #1294

This fixes cookies and devise authentication being broken as a result of
upgrading to puma 4.3.2, see https://github.com/puma/puma/issues/2132

Gemfile.lock

@@ -435,7 +435,7 @@ GEM
     pry-rails (0.3.9)
       pry (>= 0.10.4)
     public_suffix (4.0.3)
-    puma (4.3.2)
+    puma (4.3.3)
       nio4r (~> 2.0)
     pundit (2.1.0)
       activesupport (>= 3.0.0)