Fix Performance/MethodObjectAsBlock offense

There is no auto-correction for this offense, so it has been fixed
manually

Ref: https://github.com/fastruby/fast-ruby#normal-way-to-apply-method-vs-method-code

Author: tagliala

lib/ruby_llm/content.rb

@@ -43,7 +43,7 @@ def process_attachments_array_or_string(attachments)
     def process_attachments(attachments)
       if attachments.is_a?(Hash)
         # Ignores types (like :image, :audio, :text, :pdf) since we have robust MIME type detection
-        attachments.each_value(&method(:process_attachments_array_or_string))
+        attachments.each_value { |attachment| process_attachments_array_or_string(attachment) }
       else
         process_attachments_array_or_string attachments
       end