GUACAMOLE-1594: Switch to Logback 1.3.x (supports Java 8).

pom.xml

@@ -44,7 +44,7 @@
         <jersey.version>2.37</jersey.version>
         <junit.version>5.9.1</junit.version>
         <junit4.version>4.13.2</junit4.version>
-        <logback.version>1.4.4</logback.version>
+        <logback.version>1.3.4</logback.version>
         <slf4j.version>2.0.3</slf4j.version>
 
         <!-- The directory that should receive all generated dependency lists