fix(release process): upgrade maven to 3.6.2

Author: KaiSchwarz-cnic

.travis.yml

@@ -24,7 +24,13 @@ branches:
     - master
     - /^dependabot.*$/
 before_install:
-  - export MAVEN_OPTS="-Dorg.slf4j.simpleLogger.defaultLogLevel=WARN"
+  - export MAVEN_OPTS=-Dorg.slf4j.simpleLogger.defaultLogLevel=WARN
+  - export M2_HOME=~/maven
+  - export PATH=${M2_HOME}/bin:${PATH}
+install:
+  - travis_retry wget https://www-us.apache.org/dist/maven/maven-3/3.6.0/binaries/apache-maven-3.6.2-bin.tar.gz
+  - tar -xvzf apache-maven-3.6.0-bin.tar.gz
+  - sudo mv apache-maven-3.6.0 maven
 script:
   - mvn site -ntp
   - mvn package -ntp