Stop memoizing the span name

instrumentation/active_support/lib/opentelemetry/instrumentation/active_support/span_subscriber.rb

@@ -75,7 +75,7 @@ def initialize(name:, tracer:, notification_payload_transform: nil, disallowed_n
         # rubocop:enable Metrics/ParameterLists
 
         def start(name, id, payload)
-          span = @tracer.start_span(span_name(name).dup.freeze, kind: @kind)
+          span = @tracer.start_span(safe_span_name_for(name), kind: @kind)
           token = OpenTelemetry::Context.attach(
             OpenTelemetry::Trace.context_with_span(span)
           )
@@ -138,15 +138,6 @@ def sanitized_value(value)
           end
         end
 
-        def span_name(name)
-          case @name
-          when Regexp
-            safe_span_name_for(name)
-          else
-            @span_name ||= safe_span_name_for(@name)
-          end
-        end
-
         # Helper method to try an shield the span name formatter from errors
         #
         # It wraps the user supplied formatter in a rescue block and returns the original name if a StandardError is raised by the formatter

instrumentation/active_support/test/opentelemetry/instrumentation/active_support/span_subscriber_test.rb

@@ -35,11 +35,6 @@ def finish(name, id, payload)
     instrumentation.install({})
   end
 
-  it 'memoizes the span name' do
-    span, = subscriber.start('oh.hai', 'abc', {})
-    _(span.name).must_equal(notification_name)
-  end
-
   it 'uses the provided tracer' do
     subscriber = OpenTelemetry::Instrumentation::ActiveSupport::SpanSubscriber.new(
       name: 'oh.hai',