Bump logback-classic from 1.1.7 to 1.2.0 in /rl4j-examples

Bumps logback-classic from 1.1.7 to 1.2.0.

---
updated-dependencies:
- dependency-name: ch.qos.logback:logback-classic
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

rl4j-examples/pom.xml

@@ -35,7 +35,7 @@
         <java.version>1.8</java.version>
         <maven-compiler-plugin.version>3.6.1</maven-compiler-plugin.version>
         <maven.minimum.version>3.3.1</maven.minimum.version>
-        <logback.version>1.1.7</logback.version>
+        <logback.version>1.2.0</logback.version>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     </properties>