8297295: Remove ThreadGroup.allowThreadSuspension

Reviewed-by: jpai, smarks, chegar, darcy

src/java.base/share/classes/java/lang/ThreadGroup.java

@@ -700,23 +700,6 @@ public class ThreadGroup implements Thread.UncaughtExceptionHandler {
         }
     }
 
-    /**
-     * Does nothing.
-     *
-     * @return false
-     *
-     * @param b ignored
-     *
-     * @deprecated This method was originally intended for controlling suspension
-     *             in low memory conditions. It was never specified.
-     *
-     * @since   1.1
-     */
-    @Deprecated(since="1.2", forRemoval=true)
-    public boolean allowThreadSuspension(boolean b) {
-        return false;
-    }
-
     /**
      * Returns a string representation of this Thread group.
      *