Update DictionaryContainsKeyConstraint modifiers

docs/articles/nunit/writing-tests/constraints/DictionaryContainsKeyConstraint.md

@@ -20,31 +20,35 @@ Does.Not.ContainKey(object)
 ## Modifiers
 
 ```csharp
-...IgnoreCase
-...IgnoreWhiteSpace  // From version 4.2
-...Using(IEqualityComparer comparer)
-...Using(IComparer comparer)
-...Using<T>(IEqualityComparer<T> comparer)
-...Using<T>(IComparer<T> comparer)
-...Using<T>(Comparison<T> comparer)
-...Using<T>(Func<T, T, bool> comparer)
-...UsingPropertiesComparer()  // From version 4.1
-...UsingPropertiesComparer(
-      Func<PropertiesComparerConfiguration,
-           PropertiesComparerConfiguration> configure) // From version 4.4
 ...WithValue(object expectedValue)
 ```
 
+As of version 4.4.0 of NUnit the other modifiers were removed as they were non-functional.
+NUnit's `ContainKey` works the same as the `ContainsKey` method on `Dictionary`
+It uses the comparer specified when the dictionary was created.
+
 ## Examples of Use
 
 ```csharp
-IDictionary<int, int> idict = new IDictionary<int, int> { { 1, 4 }, { 2, 5 } };
+var caseSensitiveDictionary = new Dictionary<string, string>(StringComparer.Ordinal)
+{
+    ["Hello"] = "World",
+};
+
+Assert.That(caseSensitiveDictionary, Does.ContainKey("Hello"));
+Assert.That(caseSensitiveDictionary, Does.Not.ContainKey("hello"));
+
+var caseInsensitiveDictionary = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase)
+{
+    ["Hello"] = "World",
+};
+
+Assert.That(caseInsensitiveDictionary, Does.ContainKey("Hello"));
+Assert.That(caseInsensitiveDictionary, Does.ContainKey("hello"));
+Assert.That(caseInsensitiveDictionary, Does.Not.ContainKey("hallo"));
 
-Assert.That(idict, Contains.Key(1));
-Assert.That(idict, Does.ContainKey(2));
-Assert.That(idict, Does.Not.ContainKey(3));
-Assert.That(mydict, Contains.Key(myOwnObject).Using(myComparer));
-Assert.That(mydict, Does.ContainKey("Hello").WithValue("World"));
+// Note that the 'IgnoreCase' here is on the Value part, not the Key.
+Assert.That(caseInsensitiveDictionary, Does.ContainKey("hello").WithValue("world").IgnoreCase);
 ```
 
 ## See also