Use latest JRuby v9.2.18 in Travis CI builds

Author: floehopper

.travis.yml

@@ -14,7 +14,7 @@ rvm:
   - 2.6.5
   - 2.7.0
   - ruby-head
-  - jruby-9.2.14.0
+  - jruby-9.2.18.0
   - jruby-head
   - truffleruby
 gemfile:
@@ -29,7 +29,7 @@ matrix:
     - rvm: jruby-head
       gemfile: gemfiles/Gemfile.minitest.latest
       env: MOCHA_OPTIONS=debug MOCHA_RUN_INTEGRATION_TESTS=minitest
-    - rvm: jruby-9.2.14.0
+    - rvm: jruby-9.2.18.0
       gemfile: gemfiles/Gemfile.minitest.latest
       env: MOCHA_OPTIONS=debug MOCHA_RUN_INTEGRATION_TESTS=minitest
     - rvm: ruby-head