ci: no need to include java

The dependency on java was introduced in 2012 (c021cf52d8) to start
Sauce-Connect from sauce labs.

Probably at the time it was a runtime dependency, but it is no longer the case
today. It is possible that java was already not needed when db003a1460 changed
from downloading Sauce-Connect-latest.zip to sc-latest-linux.tar.gz.

Moreover, I am quite sure tests/frontend/travis/sauce_tunnel.sh no longer works
today, because tests/frontend/travis/sauce_tunnel.sh downloads from an url that
gives HTTP/404 now: sc-latest-linux.tar.gz if no longer a valid file name, we
would need to explicitly download a specific version.

.travis.yml

@@ -16,9 +16,6 @@ env:
     - secure: "WMGxFkOeTTlhWB+ChMucRtIqVmMbwzYdNHuHQjKCcj8HBEPdZLfCuK/kf4rG\nVLcLQiIsyllqzNhBGVHG1nyqWr0/LTm8JRqSCDDVIhpyzp9KpCJQQJG2Uwjk\n6/HIJJh/wbxsEdLNV2crYU/EiVO3A4Bq0YTHUlbhUqG3mSCr5Ec="
     - secure: "gejXUAHYscbR6Bodw35XexpToqWkv2ifeECsbeEmjaLkYzXmUUNWJGknKSu7\nEUsSfQV8w+hxApr1Z+jNqk9aX3K1I4btL3cwk2trnNI8XRAvu1c1Iv60eerI\nkE82Rsd5lwUaMEh+/HoL8ztFCZamVndoNgX7HWp5J/NRZZMmh4g="
 
-jdk:
-  - oraclejdk6
-
 notifications:
   irc:
     channels:

tests/frontend/travis/sauce_tunnel.sh

@@ -1,5 +1,11 @@
 #!/bin/bash
 # download and unzip the sauce connector
+#
+# ACHTUNG: as of 2019-12-21, downloading sc-latest-linux.tar.gz does not work.
+#          It is necessary to explicitly download a specific version, for
+#          example https://saucelabs.com/downloads/sc-4.5.4-linux.tar.gz
+#          Supported versions are currently listed at:
+#          https://wiki.saucelabs.com/display/DOCS/Downloading+Sauce+Connect+Proxy
 curl https://saucelabs.com/downloads/sc-latest-linux.tar.gz > /tmp/sauce.tar.gz
 tar zxf /tmp/sauce.tar.gz --directory /tmp
 mv /tmp/sc-*-linux /tmp/sauce_connect