[#1696] Fix link in readme of tests

The readme file in the tests module now points to the section in the developer
guide that explains how to build the docker images from source.

Fixes #1696 

Signed-off-by: Abel Buechner-Mihaljevic <Abel.Buechner@bosch-si.com>

tests/readme.md

@@ -7,7 +7,7 @@ This module contains integration tests for Hono. The tests are executed against
 In order to run the tests you will need the following:
 
 * a working *Docker Engine* installation (either local or on a separate host)
-* the Docker images of the Hono components. See the [Getting Started guide on the project web site](https://www.eclipse.org/hono/getting-started/) for instructions on building the Docker images.
+* the Docker images of the Hono components. See the [Developer Guide on the project web site](https://www.eclipse.org/hono/docs/dev-guide/building_hono/) for instructions on building the Docker images.
 
 ## Running the Tests