Update dependency org.slf4j:slf4j-simple to v2.0.15

Author: renovate[bot]

pom.xml

@@ -370,7 +370,7 @@
         <dependency>
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-simple</artifactId>
-            <version>2.0.9</version>
+            <version>2.0.15</version>
             <scope>test</scope>
         </dependency>
         <!-- This needs to be before Spigot because MockBukkit will fail otherwise. -->