Update Maven compiler source and target versions to 11 in pom.xml, aligning with project requirements.

Author: mbasadi

pom.xml

@@ -15,8 +15,8 @@
     <url>https://github.com/notificationapi-com/notificationapi-java-server-sdk</url>
 
     <properties>
-        <maven.compiler.source>17</maven.compiler.source>
-        <maven.compiler.target>17</maven.compiler.target>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     </properties>