Remove unused predicate

Author: smowton

java/ql/lib/semmle/code/java/Statement.qll

@@ -450,13 +450,6 @@ class SwitchCase extends Stmt, @case {
     result = this.getSwitch().getExpr() or result = this.getSwitchExpr().getExpr()
   }
 
-  /**
-   * Gets the `i`th case in this case's switch block.
-   */
-  SwitchCase getSiblingCase(int i) {
-    result = this.getSwitch().getCase(i) or result = this.getSwitchExpr().getCase(i)
-  }
-
   /**
    * Gets this case's ordinal in its switch block.
    */