Remove incorrect Decrypt() documentation

Fixes #8322

Author: wenz

xml/System.IO/File.xml

@@ -1579,7 +1579,7 @@ An I/O error occurred.</exception>
  >
  > Use of this API in .NET Core is not recommended; it is included to enable portability for applications that move to .NET Core but still explicitly target Windows.
 
- The <xref:System.IO.File.Decrypt%2A> method requires exclusive access to the file being decrypted, and will raise an exception if another process is using the file. If the file is not encrypted, <xref:System.IO.File.Decrypt%2A> will return a nonzero value, which indicates success.
+ The <xref:System.IO.File.Decrypt%2A> method requires exclusive access to the file being decrypted, and will raise an exception if another process is using the file.
 
  Both the <xref:System.IO.File.Encrypt%2A> method and the <xref:System.IO.File.Decrypt%2A> method use the cryptographic service provider (CSP) installed on the computer and the file encryption keys of the process calling the method.