Update logback-classic from 1.2.13 to 1.3.15

This is needed to support JPMS, because 1.3.x is
the first release including the module-info file.

Author: OpenHelios

logback-ecs-encoder/pom.xml

@@ -38,7 +38,7 @@
         <dependency>
             <groupId>ch.qos.logback</groupId>
             <artifactId>logback-classic</artifactId>
-            <version>1.2.13</version>
+            <version>1.3.15</version>
             <scope>provided</scope>
         </dependency>
         <dependency>
@@ -50,4 +50,4 @@
         </dependency>
     </dependencies>
 
-</project>
+</project>