fix(travis): Don't run e2e tests with jQuery twice

The e2e tests were set up to be run twice; once with the latest supported
jQuery and once with jQuery 2.1. However, the latest jQuery was used in both
cases. The initial plan was to just run integration tests with the latest
jQuery and leave regression testing for jQuery 2.1 to unit tests as they're
way faster. This commit removes the jQuery 2.1 e2e tests entry.

This commit has been landed on master a few months ago but I forgot to
backport it to v1.5.x.

(cherry-picked from 038d990)

Author: mgol

.travis.yml

@@ -19,7 +19,6 @@ env:
     - JOB=unit BROWSER_PROVIDER=saucelabs
     - JOB=docs-e2e BROWSER_PROVIDER=saucelabs
     - JOB=e2e TEST_TARGET=jqlite BROWSER_PROVIDER=saucelabs
-    - JOB=e2e TEST_TARGET=jquery-2.1 BROWSER_PROVIDER=saucelabs
     - JOB=e2e TEST_TARGET=jquery BROWSER_PROVIDER=saucelabs
   global:
     - CXX=g++-4.8  # node 4 likes the G++ v4.8 compiler