Update summary of EquivalencyValidator.cs (#1991)

As discussed in person with @dennisdoomen the summary was not strictly correct.

Src/FluentAssertions/Equivalency/EquivalencyValidator.cs

@@ -5,7 +5,7 @@
 namespace FluentAssertions.Equivalency;
 
 /// <summary>
-/// Is responsible for validating the equality of one or more properties of a subject with another object.
+/// Is responsible for validating the equivalency of a subject with another object.
 /// </summary>
 public class EquivalencyValidator : IEquivalencyValidator
 {