Update logging article in DocC documentation. (#1672)

Co-authored-by: Sichan Yoo <chanyoo@amazon.com>

Sources/Core/AWSSDKForSwift/Documentation.docc/logging.md

@@ -3,14 +3,15 @@
 The AWS SDK for Swift uses SwiftLog for high performant logging.  Many of our calls are issued to the `debug` level of output, which are disabled in the console by default.  To see debug output to your console, you can add the following code to your application in a place where you know that the code will be called once and only once:
 ```swift
 import ClientRuntime
-SDKLoggingSystem.initialize(logLevel: .debug)
+SDKLoggingSystem().initialize(logLevel: .debug)
 ```
 
-Alternatively, if you need finer grain control of instances of SwiftLog, you can call `SDKLoggingSystem.add` to control specific instances of the log handler.  For example:
+Alternatively, if you need finer grain control of instances of SwiftLog, you can call `SDKLoggingSystem::add` to control specific instances of the log handler.  For example:
 ```swift
 import ClientRuntime
 
-SDKLoggingSystem.add(logHandlerFactory: S3ClientLogHandlerFactory(logLevel: .debug))
-SDKLoggingSystem.add(logHandlerFactory: CRTClientEngineLogHandlerFactory(logLevel: .info))
-SDKLoggingSystem.initialize()
+let system = SDKLoggingSystem()
+system.add(logHandlerFactory: S3ClientLogHandlerFactory(logLevel: .debug))
+system.add(logHandlerFactory: CRTClientEngineLogHandlerFactory(logLevel: .info))
+system.initialize()
 ```