remove unnecessary class - jtreg comment is enough to run the test

Author: nizarbenalla

test/jdk/tools/sincechecker/testjavabase/CheckSince_javaBase.java

@@ -31,7 +31,4 @@
  *          jdk.compiler/com.sun.tools.javac.util
  *          jdk.compiler/com.sun.tools.javac.code
  * @run main SinceChecker java.base
- */
-
-public class CheckSince_javaBase {
-}
+ */