Remove uses of Timeout.timeout from Server (teamcapybara#2016)

* Don't use Timeout.timeout in Server#wait_for_pending_requests

I expect this to be equivalent since it rases the same error and has the
same pattern of sleeps.

* Don't use Timeout.timeout in Server#boot

I expect this to be equivalent since it rases the same error and has the
same pattern of sleeps.

I don't know of any problems caused by using timeout here, instead I've
converted this for consistency and so that that there are no longer any
uses of `Timeout.timeout` within the codebase.

lib/capybara/server.rb

@@ -90,9 +90,13 @@ def responsive?
     end
 
     def wait_for_pending_requests
-      Timeout.timeout(60) { sleep(0.01) while pending_requests? }
-    rescue Timeout::Error
-      raise "Requests did not finish in 60 seconds"
+      start_time = Capybara::Helpers.monotonic_time
+      while pending_requests?
+        if (Capybara::Helpers.monotonic_time - start_time) > 60
+          raise "Requests did not finish in 60 seconds"
+        end
+        sleep 0.01
+      end
     end
 
     def boot
@@ -103,11 +107,15 @@ def boot
           Capybara.server.call(middleware, port, host)
         end
 
-        Timeout.timeout(60) { @server_thread.join(0.1) until responsive? }
+        start_time = Capybara::Helpers.monotonic_time
+        until responsive?
+          if (Capybara::Helpers.monotonic_time - start_time) > 60
+            raise "Rack application timed out during boot"
+          end
+          @server_thread.join(0.1)
+        end
       end
-    rescue Timeout::Error
-      raise "Rack application timed out during boot"
-    else
+
       self
     end