Fix "complementary" typo in Span`1.xml (#2502)

Although it's true that the `Memory` type is supplied *free of charge*, the intended meaning here is that it *works together* with `Span`.

Author: taradinoc

xml/System/Span`1.xml

@@ -41,7 +41,7 @@
 `Span<T>` is a [ref struct](~/docs/csharp/language-reference/keywords/ref.md#ref-struct-types) that is allocated on the stack rather than on the managed heap. Ref struct types have a number of restrictions to ensure that they cannot be promoted to the managed heap, including that they can't be boxed, they can't be assigned to variables of type <xref:System.Object>, `dynamic` or to any interface type, they can't be fields in a reference type, and they can't be used across `await` and `yield` boundaries. In addition, calls to two methods, <xref:System.Span%601.Equals(System.Object)> and <xref:System.Span%601.GetHashCode%2A>, throw a <xref:System.NotSupportedException>. 
 
 > [!IMPORTANT]
-> Because it is a stack-only type, `Span<T>` is unsuitable for many scenarios that require storing references to buffers on the heap. This is true, for example, of routines that make asynchronous method calls. For such scenarios, you can use the complimentary <xref:System.Memory%601?displayProperty=nameWithType> and <xref:System.ReadOnlyMemory%601?displayProperty=nameWithType> types.
+> Because it is a stack-only type, `Span<T>` is unsuitable for many scenarios that require storing references to buffers on the heap. This is true, for example, of routines that make asynchronous method calls. For such scenarios, you can use the complementary <xref:System.Memory%601?displayProperty=nameWithType> and <xref:System.ReadOnlyMemory%601?displayProperty=nameWithType> types.
 
 For spans that represent immutable or read-only structures, use <xref:System.ReadOnlySpan%601?displayProperty=nameWithType>.