[TRIVIAL] Remove deprecated sudo setting

[Travis are now recommending removing the sudo tag.](https://blog.travis-ci.com/2018-11-19-required-linux-infrastructure-migration)
diff --git a/.travis.yml b/.travis.yml
index 7eb275a..bdcbfd1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -13,7 +13,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-sudo: false
 dist: trusty
 
 language: java