fix: loosen version constraints to support old versions

Author: joker1007

instrumentation/rdkafka/lib/opentelemetry/instrumentation/rdkafka/instrumentation.rb

@@ -11,7 +11,7 @@ module Rdkafka
       class Instrumentation < OpenTelemetry::Instrumentation::Base
         compatible do
           gem_version = Gem::Version.new(::Rdkafka::VERSION)
-          Gem::Requirement.new('>= 0.20.0').satisfied_by?(gem_version)
+          Gem::Requirement.new('>= 0.10.0').satisfied_by?(gem_version)
         end
 
         install do |_config|

instrumentation/rdkafka/lib/opentelemetry/instrumentation/rdkafka/patches/consumer.rb

@@ -42,7 +42,8 @@ def each
             end
           end
 
-          # each_batch method is deleted in rdkafka 0.20.0
+          # each_batch method is deleted in rdkafka-ruby-0.20.0
+          # But, rdkafka-ruby-0.19.x and 0.18.x are still maintained
           if Gem::Version.new(::Rdkafka::VERSION) < Gem::Version.new('0.20.0')
             def each_batch(max_items: 100, bytes_threshold: Float::INFINITY, timeout_ms: 250, yield_on_error: false, &block)
               super do |messages, error|