C++: Fix more QLDoc.

Author: MathiasVP

cpp/ql/lib/semmle/code/cpp/ir/implementation/EdgeKind.qll

@@ -92,7 +92,7 @@ class CaseEdge extends EdgeKind, TCaseEdge {
   final string getMaxValue() { result = maxValue }
 
   /**
-   * Gets the unique value of ther switch expression for which control will
+   * Gets the unique value of the switch expression for which control will
    * flow along this edge, if any.
    */
   final string getValue() {