Revert "Add deprecation-notice to rule CA2109" (#32980)

Author: Youssef1313

docs/fundamentals/code-analysis/quality-rules/ca2109.md

@@ -24,11 +24,6 @@ ms.author: gewarren
 
 A public or protected event-handling method was detected.
 
-> [!NOTE]
-> This rule has been deprecated. It last shipped with Microsoft.CodeAnalysis.Analyzers v3.3.0.
->
-> The rule was removed because the threat that the analyzer warned about (an untrusted intermediary hooking a privileged event handler to a privileged event invoker) hasn't existed since .NET Framework 4.5.
-
 ## Rule description
 
 An externally visible event-handling method presents a security issue that requires review.