Fix HTTP_S3_Download compile warning (#1195)

* Fix xPlatformIsNetworkUp() is undeclared warning
* Fix cast const type warning

Co-authored-by: Soren Ptak <ptaksoren@gmail.com>
Co-authored-by: Rahul Kar <118818625+kar-rahul-aws@users.noreply.github.com>

FreeRTOS-Plus/Demo/coreHTTP_Windows_Simulator/HTTP_S3_Download/DemoTasks/S3DownloadHTTPExample.c

@@ -476,7 +476,7 @@ static JSONStatus_t prvParseCredentials( HTTPResponse_t * pxResponse,
  * @return pdPASS on success, pdFAIL on failure.
  */
 static BaseType_t prvGetTemporaryCredentials( TransportInterface_t * pxTransportInterface,
-                                              const char * pcDateISO8601,
+                                              char * pcDateISO8601,
                                               size_t xDateISO8601Len,
                                               HTTPResponse_t * pxResponse,
                                               SigV4Credentials_t * pxSigvCreds );
@@ -582,6 +582,10 @@ void vStartSimpleHTTPDemo( void )
 
 /*-----------------------------------------------------------*/
 
+extern BaseType_t xPlatformIsNetworkUp( void );
+
+/*-----------------------------------------------------------*/
+
 /**
  * @brief Entry point of the demo.
  *
@@ -1177,7 +1181,7 @@ static BaseType_t prvDownloadS3ObjectFile( const TransportInterface_t * pxTransp
 }
 
 static BaseType_t prvGetTemporaryCredentials( TransportInterface_t * pxTransportInterface,
-                                              const char * pcDateISO8601,
+                                              char * pcDateISO8601,
                                               size_t xDateISO8601Len,
                                               HTTPResponse_t * pxResponse,
                                               SigV4Credentials_t * pxSigvCreds )