fix(tests): unbreak main - disambiguate Count overload after IsEqualTo wrappers (#5751) (#5759)

* fix(tests): disambiguate Count overload broken by IsEqualTo wrappers (#5751)

Chained_Collection_Assertions_WithStrings called
.Count(c => c.IsEqualTo(3)) on string[]. Before #5751 this failed to
bind to the per-item filter overload (int-vs-string mismatch on
IsEqualTo) and resolved to the inline-count assertion form, returning
a chainable assertion. After #5751 added IsEqualTo<TValue, TOther>
with implicit-conversion fallback, both overloads compile and
resolution picks the per-item filter, which returns
CollectionCountSource<,> -- a count source without .And -- breaking
.And.Contains("Bob") with CS1061.

Mirror the int test (Chained_Collection_Assertions) and use
.Count().IsEqualTo(3) so the resulting assertion is the chainable
CollectionCountEqualsAssertion regardless of TItem.

* fix(tests): tighten Count overload comment

Author: thomhurst

TUnit.Assertions.Tests/CollectionAssertionTests.cs

@@ -263,10 +263,10 @@ public async Task Chained_Collection_Assertions_WithStrings()
     {
         var names = new[] { "Alice", "Bob", "Charlie" };
 
-        // For non-int collections, Count(c => c.IsEqualTo(3)) works unambiguously
+        // Count(predicate) is the per-item filter overload and returns a source without .And.
         await Assert.That(names)
             .IsNotEmpty()
-            .And.Count(c => c.IsEqualTo(3))
+            .And.Count().IsEqualTo(3)
             .And.Contains("Bob")
             .And.DoesNotContain("Dave");
     }