Make draggable true by default - so it will be true when using Empty Constructor as well

PiperOrigin-RevId: 290121017

Author: Material Design Team

lib/java/com/google/android/material/bottomsheet/BottomSheetBehavior.java

@@ -233,7 +233,7 @@ public abstract static class BottomSheetCallback {
 
   private boolean skipCollapsed;
 
-  private boolean draggable;
+  private boolean draggable = true;
 
   @State int state = STATE_COLLAPSED;