Update JRuby version in Travis CI config

JRuby v9.2.9.0 was released at the end of Oct 2019 [1].

[1]: https://www.jruby.org/2019/10/30/jruby-9-2-9-0.html

.travis.yml

@@ -13,7 +13,7 @@ rvm:
   - 2.5.7
   - 2.6.5
   - ruby-head
-  - jruby-9.2.8.0
+  - jruby-9.2.9.0
   - jruby-head
   - truffleruby
 gemfile:
@@ -28,7 +28,7 @@ matrix:
     - rvm: jruby-head
       gemfile: gemfiles/Gemfile.minitest.latest
       env: MOCHA_OPTIONS=debug MOCHA_RUN_INTEGRATION_TESTS=minitest
-    - rvm: jruby-9.2.8.0
+    - rvm: jruby-9.2.9.0
       gemfile: gemfiles/Gemfile.minitest.latest
       env: MOCHA_OPTIONS=debug MOCHA_RUN_INTEGRATION_TESTS=minitest
     - rvm: ruby-head
@@ -106,7 +106,7 @@ matrix:
     - rvm: truffleruby
       gemfile: gemfiles/Gemfile.test-unit.latest
       env: MOCHA_OPTIONS=debug MOCHA_RUN_INTEGRATION_TESTS=test-unit
-    - rvm: jruby-9.2.8.0
+    - rvm: jruby-9.2.9.0
       gemfile: gemfiles/Gemfile.test-unit.latest
       env: MOCHA_OPTIONS=debug MOCHA_RUN_INTEGRATION_TESTS=test-unit
     - rvm: jruby-head