Fix link to the Docker ReadMe

Author: mdmintz

integrations/selenium_grid/ReadMe.md

@@ -1,6 +1,6 @@
 ## Notes on using the Selenium Grid Hub
 
-The Selenium Grid Hub allows you to distribute tests to run in parallel across multiple machines. Each machine can then run its own allocation of tests in parallel. This allows you to run an entire test suite quickly, which may be important if you have a lot of tests to run. Machines can be personal computers, data centers, or virtual machines in the cloud. You can also create your own virtual machine by using a tool such as Docker (see the [Docker_README](https://github.com/mdmintz/SeleniumBase/blob/master/Docker_README.md)).
+The Selenium Grid Hub allows you to distribute tests to run in parallel across multiple machines. Each machine can then run its own allocation of tests in parallel. This allows you to run an entire test suite quickly, which may be important if you have a lot of tests to run. Machines can be personal computers, data centers, or virtual machines in the cloud. You can also create your own virtual machine by using a tool such as Docker (see the [Docker ReadMe](https://github.com/mdmintz/SeleniumBase/blob/master/integrations/docker/ReadMe.md)).
 
 ### Running the Selenium Grid Hub