C#: Deprecate controlsBlock.

Author: aschackmull

csharp/ql/lib/semmle/code/csharp/controlflow/ControlFlowElement.qll

@@ -88,6 +88,8 @@ class ControlFlowElement extends ExprOrStmtParent, @control_flow_element {
   }
 
   /**
+   * DEPRECATED: Use `Guard` class instead.
+   *
    * Holds if basic block `controlled` is controlled by this control flow element
    * with conditional value `s`. That is, `controlled` can only be reached from
    * the callable entry point by going via the `s` edge out of *some* basic block
@@ -96,7 +98,9 @@ class ControlFlowElement extends ExprOrStmtParent, @control_flow_element {
    * `cb` records all of the possible condition blocks for this control flow element
    * that a path from the callable entry point to `controlled` may go through.
    */
-  predicate controlsBlock(BasicBlock controlled, ConditionalSuccessor s, ConditionBlock cb) {
+  deprecated predicate controlsBlock(
+    BasicBlock controlled, ConditionalSuccessor s, ConditionBlock cb
+  ) {
     cb.getLastNode() = this.getAControlFlowNode() and
     cb.edgeDominates(controlled, s)
   }