Add and apply Style/SoleNestedConditional rule

We were already applying it in most places.

.rubocop.yml

@@ -517,6 +517,9 @@ Style/RedundantSelf:
 Style/SafeNavigation:
   Enabled: true
 
+Style/SoleNestedConditional:
+  Enabled: true
+
 Style/StringLiterals:
   EnforcedStyle: double_quotes
 

app/models/comment_notifier.rb

@@ -12,8 +12,8 @@ class CommentNotifier
   private
 
     def send_comment_email
-      unless @comment.commentable.is_a?(Legislation::Annotation)
+      if !@comment.commentable.is_a?(Legislation::Annotation) && email_on_comment?
-        Mailer.comment(@comment).deliver_later if email_on_comment?
+        Mailer.comment(@comment).deliver_later
       end
     end