Apply Style/RedundantReturn rubocop rule

We were already following this pattern most of the time.

.rubocop.yml

@@ -409,6 +409,9 @@ Style/Proc:
 Style/RedundantFreeze:
   Enabled: true
 
+Style/RedundantReturn:
+  Enabled: true
+
 Style/SafeNavigation:
   Enabled: true
 

app/helpers/signature_sheets_helper.rb

@@ -26,7 +26,7 @@ module SignatureSheetsHelper
     text_help += tag(:br)
     text_help += t("admin.signature_sheets.new.text_help.required_fields_structure_note")
 
-    return text_help
+    text_help
   end
 
   def example_text_help
@@ -45,6 +45,6 @@ module SignatureSheetsHelper
     end
 
     text_example += "#{example_1}; #{example_2}"
-    return text_example
+    text_example
   end
 end

app/models/debate.rb

@@ -165,6 +165,6 @@ class Debate < ApplicationRecord
   def self.debates_orders(user)
     orders = %w[hot_score confidence_score created_at relevance]
     orders << "recommendations" if Setting["feature.user.recommendations_on_debates"] && user&.recommended_debates
-    return orders
+    orders
   end
 end

app/models/i18n_content.rb

@@ -40,7 +40,7 @@ class I18nContent < ApplicationRecord
     return output.update({ path => input }) unless input.is_a? Hash
 
     input.map { |key, value| flat_hash(value, [path, key].compact.join("."), output) }
-    return output
+    output
   end
 
   def self.content_for(tab)

app/models/proposal.rb

@@ -243,7 +243,7 @@ class Proposal < ApplicationRecord
   def self.proposals_orders(user)
     orders = %w[hot_score confidence_score created_at relevance archival_date]
     orders << "recommendations" if Setting["feature.user.recommendations_on_proposals"] && user&.recommended_proposals
-    return orders
+    orders
   end
 
   def skip_user_verification?

app/models/signature_sheet.rb

@@ -52,11 +52,11 @@ class SignatureSheet < ApplicationRecord
 
     def parse_postal_code(required_fields_to_verify)
       if Setting.force_presence_date_of_birth? && Setting.force_presence_postal_code?
-        return required_fields_to_verify[2]
+        required_fields_to_verify[2]
       elsif Setting.force_presence_postal_code?
-        return required_fields_to_verify[1]
+        required_fields_to_verify[1]
       else
-        return nil
+        nil
       end
     end
 end

spec/shared/features/nested_documentable.rb

@@ -308,7 +308,7 @@ def documentable_redirected_to_resource_show_or_navigate_to
   find("a", text: "Not now, go to my proposal")
   click_on "Not now, go to my proposal"
 rescue
-  return
+  nil
 end
 
 def documentable_attach_new_file(path, success = true)

spec/shared/features/nested_imageable.rb

@@ -254,7 +254,7 @@ def imageable_redirected_to_resource_show_or_navigate_to
   find("a", text: "Not now, go to my proposal")
   click_on "Not now, go to my proposal"
 rescue
-  return
+  nil
 end
 
 def imageable_attach_new_file(_imageable_factory_name, path, success = true)