Update summary for CryptographicOperations documentation (#11801)

CryptographicOperations was documented as doing exclusively side-channel resistant things. Let's relax the description a little since we introduced HashData and HmacData.

Author: vcsjones

xml/System.Security.Cryptography/CryptographicOperations.xml

@@ -40,7 +40,7 @@
   </Base>
   <Interfaces />
   <Docs>
-    <summary>Provides methods for use in working with cryptography to reduce the risk of side-channel information leakage.</summary>
+    <summary>Provides methods for common cryptographic operations and reducing side-channel information leakage.</summary>
     <remarks>To be added.</remarks>
   </Docs>
   <Members>