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
...

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Author: dependabot[bot]

rl4j-examples/pom.xml

@@ -10,7 +10,7 @@
     <properties>
         <nd4j.version>1.0.0-M1.1</nd4j.version>
         <rl4j.version>1.0.0-M1.1</rl4j.version>
-        <logback.version>1.1.7</logback.version>
+        <logback.version>1.2.0</logback.version>
         <java.version>1.8</java.version>
         <maven-compiler-plugin.version>3.8.1</maven-compiler-plugin.version>
         <maven.minimum.version>3.3.1</maven.minimum.version>