Remove UnsupportedOsPlatform from CryptoConfig as a utility class (#43611)

* Remove UnsupportedOsPlatform from CryptoConfig as it is a safe utility class

* Clean up the other references

Author: lewing

src/libraries/System.Security.Cryptography.Algorithms/ref/System.Security.Cryptography.Algorithms.cs

@@ -96,7 +96,6 @@ protected AsymmetricSignatureFormatter() { }
         public abstract void SetHashAlgorithm(string strName);
         public abstract void SetKey(System.Security.Cryptography.AsymmetricAlgorithm key);
     }
-    [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("browser")]
     public partial class CryptoConfig
     {
         public CryptoConfig() { }

src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/CryptoConfig.cs

@@ -8,11 +8,9 @@
 using System.Globalization;
 using System.Reflection;
 using System.Runtime.InteropServices;
-using System.Runtime.Versioning;
 
 namespace System.Security.Cryptography
 {
-    [UnsupportedOSPlatform("browser")]
     public class CryptoConfig
     {
         private const string AssemblyName_Cng = "System.Security.Cryptography.Cng";