Expand SystemApi annotation for generating system api

Metalava apparently normalizes the SystemApi annotation that was
previously used to the form that this change uses so this is
effectively a no-op. However, this does make this code more
self-consistent and also matches the form that is used in the framework
defaults for the mainline modules.

Test: m checkapi
Bug: 155164730
Change-Id: Ic99b7333730ed8b918d8af72ae7bd6a851c2093a

java/sdk_library.go

@@ -141,7 +141,7 @@ var (
 		apiFilePrefix:  "system-",
 		moduleSuffix:   sdkSystemApiSuffix,
 		sdkVersion:     "system_current",
-		droidstubsArgs: []string{"-showAnnotation android.annotation.SystemApi"},
+		droidstubsArgs: []string{"-showAnnotation android.annotation.SystemApi\\(client=android.annotation.SystemApi.Client.PRIVILEGED_APPS\\)"},
 	})
 	apiScopeTest = initApiScope(&apiScope{
 		name:           "test",