Add Performance/BlockGivenWithExplicitBlock rule

We don't need to use `block_given?` since we specifically pass the block
parameter, particularly since we added the Style/ExplicitBlockArgument
rule in commit a102f3f0a.

.rubocop.yml

@@ -205,6 +205,9 @@ Lint/UselessAssignment:
 Lint/Void:
   Enabled: true
 
+Performance/BlockGivenWithExplicitBlock:
+  Enabled: true
+
 Performance/CompareWithBlock:
   Enabled: true
 

app/components/concerns/header.rb

@@ -17,7 +17,7 @@ module Header
                   end
 
     tag.header do
-      safe_join([before, content_tag(heading_tag, title), (capture(&block) if block_given?)].compact)
+      safe_join([before, content_tag(heading_tag, title), (capture(&block) if block)].compact)
     end
   end