Update javalin.version to v6.4.0

Author: renovate[bot]

pom.xml

@@ -10,7 +10,7 @@
 
     <properties>
         <slf4j-api.version>2.0.13</slf4j-api.version>
-        <javalin.version>6.3.0</javalin.version>
+        <javalin.version>6.4.0</javalin.version>
     </properties>
     <build>
         <plugins>