Remove allow_restart argument

I initially added this thinking it may make it easier for testing
and/or experimentation, but after feedback from review, let's go without
it for now -- we can always re-add later.

lib/datadog/core/remote/worker.rb

@@ -19,12 +19,12 @@ def initialize(interval:, &block)
           @block = block
         end
 
-        def start(allow_restart: false)
+        def start
           Datadog.logger.debug { 'remote worker starting' }
 
           acquire_lock
 
-          if @stop_requested && !allow_restart
+          if @stop_requested
             Datadog.logger.debug('remote worker: refusing to restart after previous stop')
             return
           end

spec/datadog/core/remote/worker_spec.rb

@@ -77,18 +77,6 @@
       worker.start
       expect(worker.instance_variable_get(:@started)).to be false
     end
-
-    context 'when calling start with allow_restart: true' do
-      it 'restarts the worker after being stopped once' do
-        worker.start
-        expect(worker.instance_variable_get(:@started)).to be true
-
-        worker.stop
-
-        worker.start(allow_restart: true)
-        expect(worker.instance_variable_get(:@started)).to be true
-      end
-    end
   end
 
   describe '#stop' do