delete dead code

buildSrc/src/main/groovy/airbyte-python-docker.gradle

@@ -9,8 +9,6 @@ class AirbytePythonDockerConfiguration {
 class AirbytePythonDockerPlugin implements Plugin<Project> {
 
     void apply(Project project) {
-        def extension = project.extensions.create('airbytePythonDocker', AirbytePythonDockerConfiguration)
-
         project.task('airbytePythonDockerApply', type: Exec) {
             /*
             Install the dependencies, run the tests, and run static analysis from a docker container