Align class name with field name

config/initializers/metrics.rb

@@ -12,7 +12,7 @@ if Gitlab::Metrics.enabled?
 
   Gitlab::Application.configure do |config|
     config.middleware.use(Gitlab::Metrics::RackMiddleware)
-    config.middleware.use(Gitlab::Middleware::ProxyTiming)
+    config.middleware.use(Gitlab::Middleware::ProxyFlightTime)
   end
 
   Sidekiq.configure_server do |config|

lib/gitlab/middleware/proxy_flight_time.rb

@@ -4,7 +4,7 @@
 
 module Gitlab
   module Middleware
-    class ProxyTiming
+    class ProxyFlightTime
       def initialize(app)
         @app = app
       end