Revert unnecessary exists statement

Author: smowton

java/ql/lib/semmle/code/java/controlflow/internal/GuardsLogic.qll

@@ -55,13 +55,9 @@ predicate implies_v1(Guard g1, boolean b1, Guard g2, boolean b2) {
     )
   )
   or
-  exists(DefaultCase sc | g1 = sc |
-    sc.getSwitch().getAConstCase() = g2 and b1 = true and b2 = false
-  )
+  g1.(DefaultCase).getSwitch().getAConstCase() = g2 and b1 = true and b2 = false
   or
-  exists(DefaultCase sc | g1 = sc |
-    sc.getSwitchExpr().getAConstCase() = g2 and b1 = true and b2 = false
-  )
+  g1.(DefaultCase).getSwitchExpr().getAConstCase() = g2 and b1 = true and b2 = false
   or
   exists(MethodCall check, int argIndex | check = g1 |
     conditionCheckArgument(check, argIndex, _) and