updates gradle to 6.1.1 and changes used jdks in travis

Author: kmindi

.travis.yml

@@ -1,12 +1,12 @@
 language: java
 jdk:
+  - openjdk8
   - oraclejdk9
-  - oraclejdk10
+  - openjdk9
   - oraclejdk11
-  - oraclejdk12
+  - openjdk11
   - oraclejdk13
-  - oraclejdk14
-  - oraclejdk15
+  - openjdk13
 addons:
   sonarcloud:
     organization: "kmindi-github" # the key of the org you chose at step #3

gradle/wrapper/gradle-wrapper.properties

@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.0-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.1.1-all.zip