Remove unused build matrix from Travis in order to speed up the feedback loop

Author: JavierCane

.travis.yml

@@ -1,13 +1,10 @@
 language: java
 
 jdk:
-  - openjdk8
   - openjdk11
-  - oraclejdk11
 
 os:
   - linux
-  - osx
 
 before_cache:
   - rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
@@ -18,11 +15,6 @@ cache:
     - $HOME/.gradle/caches/
     - $HOME/.gradle/wrapper/
 
-# Run commands before TravisCI install step only in some cases
-# More info: https://docs.travis-ci.com/user/multi-os/#example-multi-os-build-matrix
-before_install:
-  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update; fi
-
 # Override default install process on TravisCI
 # Avoid default `gradlew assemble` execution. Be explicit about it on the `script` section.
 # More info: https://github.com/travis-ci/travis-ci/issues/8667
@@ -32,4 +24,4 @@ install: true
 # Compile before running the tests in order to easily check which task could be failing.
 script:
   - ./gradlew assemble --warning-mode all
-  - ./gradlew check --warning-mode all
+  - ./gradlew check --warning-mode all