[downsizing] remove jsonshema/tests dir (#327)

Author: joeyzhao2018

Dockerfile

@@ -18,3 +18,4 @@ RUN find ./python/lib/$runtime/site-packages -name \*.pyc -delete
 # installs it, while it's already provided by the Lambda Runtime.
 RUN rm -rf ./python/lib/$runtime/site-packages/botocore*
 RUN rm -rf ./python/lib/$runtime/site-packages/setuptools
+RUN rm -rf ./python/lib/$runtime/site-packages/jsonschema/tests