[docs] Fix warnings about undocumented default constructors (#6151)

hal/src/generate/FRCNetComm.java.in

@@ -9,7 +9,7 @@ package edu.wpi.first.hal;
 /**
  * JNI wrapper for library <b>FRC_NetworkCommunication</b><br>.
  */
-public class FRCNetComm {
+public final class FRCNetComm {
   /**
    * Resource type from UsageReporting.
    */
@@ -31,4 +31,7 @@ ${usage_reporting_types}
 
 ${usage_reporting_instances}
   }
+
+  /** Utility class. */
+  private FRCNetComm() {}
 }