updated to reflect that SecureString is only not encrypted on non-Windows systems (#4034)

Author: SteveL-MSFT

reference/6/Microsoft.PowerShell.Security/ConvertFrom-SecureString.md

@@ -39,7 +39,7 @@ If no key is specified, the Windows Data Protection API (DPAPI) is used to encry
 
 > [!NOTE]
 > Note that per [DotNet](/dotnet/api/system.security.securestring?view=netcore-2.1#remarks), the
-> contents of a SecureString are not encrypted.
+> contents of a SecureString are not encrypted on non-Windows systems.
 
 ## EXAMPLES
 

reference/6/Microsoft.PowerShell.Security/ConvertTo-SecureString.md

@@ -48,7 +48,7 @@ If the standard string being converted was encrypted with **ConvertFrom-SecureSt
 
 > [!NOTE]
 > Note that per [DotNet](/dotnet/api/system.security.securestring?view=netcore-2.1#remarks), the
-> contents of a SecureString are not encrypted.
+> contents of a SecureString are not encrypted on non-Windows systems.
 
 ## EXAMPLES