Remove old travis files; update compatibility tests link to gha

Author: dpkp

.travis.yml

@@ -16,6 +16,6 @@ Although kafka-python is tested and expected to work on recent broker versions,
 not all features are supported. Specifically, authentication codecs, and
 transactional producer/consumer support are not fully implemented. PRs welcome!
 
-kafka-python is tested on python 2.7, 3.4, 3.7, 3.8 and pypy2.7.
+kafka-python is tested on python 2.7, and 3.8-3.12.
 
-Builds and tests via Travis-CI.  See https://travis-ci.org/dpkp/kafka-python
+Builds and tests via Github Actions Workflows.  See https://github.com/dpkp/kafka-python/actions