Fix predicate nullability annotation (#7176)

Author: Evangelink

src/TestFramework/TestFramework/Assertions/Assert.Contains.cs

@@ -192,7 +192,7 @@ public static T ContainsSingle<T>(Func<T, bool> predicate, IEnumerable<T> collec
     /// Users shouldn't pass a value for this parameter.
     /// </param>
     /// <returns>The item that matches the predicate.</returns>
-    public static object? ContainsSingle(Func<object, bool> predicate, IEnumerable collection, string? message = "", [CallerArgumentExpression(nameof(predicate))] string predicateExpression = "", [CallerArgumentExpression(nameof(collection))] string collectionExpression = "")
+    public static object? ContainsSingle(Func<object?, bool> predicate, IEnumerable collection, string? message = "", [CallerArgumentExpression(nameof(predicate))] string predicateExpression = "", [CallerArgumentExpression(nameof(collection))] string collectionExpression = "")
     {
         object? firstMatch = null;
         int matchCount = 0;

src/TestFramework/TestFramework/PublicAPI/PublicAPI.Unshipped.txt

@@ -43,6 +43,7 @@ Microsoft.VisualStudio.TestTools.UnitTesting.Assert.AssertGenericIsExactInstance
 Microsoft.VisualStudio.TestTools.UnitTesting.Assert.AssertGenericIsNotExactInstanceOfTypeInterpolatedStringHandler<TArg>
 Microsoft.VisualStudio.TestTools.UnitTesting.Assert.AssertIsExactInstanceOfTypeInterpolatedStringHandler
 Microsoft.VisualStudio.TestTools.UnitTesting.Assert.AssertIsNotExactInstanceOfTypeInterpolatedStringHandler
+static Microsoft.VisualStudio.TestTools.UnitTesting.Assert.ContainsSingle(System.Func<object?, bool>! predicate, System.Collections.IEnumerable! collection, string? message = "", string! predicateExpression = "", string! collectionExpression = "") -> object?
 static Microsoft.VisualStudio.TestTools.UnitTesting.Assert.IsExactInstanceOfType(object? value, System.Type? expectedType, string? message = "", string! valueExpression = "") -> void
 static Microsoft.VisualStudio.TestTools.UnitTesting.Assert.IsExactInstanceOfType(object? value, System.Type? expectedType, ref Microsoft.VisualStudio.TestTools.UnitTesting.Assert.AssertIsExactInstanceOfTypeInterpolatedStringHandler message, string! valueExpression = "") -> void
 static Microsoft.VisualStudio.TestTools.UnitTesting.Assert.IsExactInstanceOfType<T>(object? value, string? message = "", string! valueExpression = "") -> T
@@ -52,4 +53,3 @@ static Microsoft.VisualStudio.TestTools.UnitTesting.Assert.IsNotExactInstanceOfT
 static Microsoft.VisualStudio.TestTools.UnitTesting.Assert.IsNotExactInstanceOfType<T>(object? value, string? message = "", string! valueExpression = "") -> void
 static Microsoft.VisualStudio.TestTools.UnitTesting.Assert.IsNotExactInstanceOfType<T>(object? value, ref Microsoft.VisualStudio.TestTools.UnitTesting.Assert.AssertGenericIsNotExactInstanceOfTypeInterpolatedStringHandler<T> message, string! valueExpression = "") -> void
 static Microsoft.VisualStudio.TestTools.UnitTesting.Assert.ContainsSingle(System.Collections.IEnumerable! collection, string? message = "", string! collectionExpression = "") -> object?
-static Microsoft.VisualStudio.TestTools.UnitTesting.Assert.ContainsSingle(System.Func<object!, bool>! predicate, System.Collections.IEnumerable! collection, string? message = "", string! predicateExpression = "", string! collectionExpression = "") -> object?

test/UnitTests/TestFramework.UnitTests/Assertions/AssertTests.Contains.cs

@@ -1419,7 +1419,7 @@ public void ContainsSinglePredicate_InNonGenericCollection_NoMessage_OneItemMatc
         var collection = new ArrayList { 1, 2, 3, 4, 5, "a" };
 
         // Act
-        object? result = Assert.ContainsSingle(x => x.Equals(3), collection);
+        object? result = Assert.ContainsSingle(x => x!.Equals(3), collection);
 
         // Assert
         result.Should().Be(3);