Check api level before clearing shortcut items

[AndrewJack]

Check api level before calling removeAllDynamicShortcuts()

Fix crash:

java.lang.RuntimeException Could not invoke ReactAppShortcuts.clearShortcutItems 
    BaseJavaModule.java:382 com.facebook.react.bridge.BaseJavaModule$JavaMethod.invoke
    JavaModuleWrapper.java:138 com.facebook.react.cxxbridge.JavaModuleWrapper.invoke
    NativeRunnable.java:-2 com.facebook.react.bridge.queue.NativeRunnable.run
    Handler.java:733 android.os.Handler.handleCallback
    Handler.java:95 android.os.Handler.dispatchMessage
    MessageQueueThreadHandler.java:31 com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage
    Looper.java:136 android.os.Looper.loop
    MessageQueueThreadImpl.java:208 com.facebook.react.bridge.queue.MessageQueueThreadImpl$3.run
    Thread.java:841 java.lang.Thread.run

Caused: java.lang.NoClassDefFoundError android.content.pm.ShortcutManager 
    AppShortcutsModule.java:121 com.reactNativeQuickActions.AppShortcutsModule.clearShortcutItems
    Method.java:-2 java.lang.reflect.Method.invokeNative
    Method.java:515 java.lang.reflect.Method.invoke
    BaseJavaModule.java:368 com.facebook.react.bridge.BaseJavaModule$JavaMethod.invoke
    JavaModuleWrapper.java:138 com.facebook.react.cxxbridge.JavaModuleWrapper.invoke
    NativeRunnable.java:-2 com.facebook.react.bridge.queue.NativeRunnable.run
    Handler.java:733 android.os.Handler.handleCallback
    Handler.java:95 android.os.Handler.dispatchMessage
    MessageQueueThreadHandler.java:31 com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage
    Looper.java:136 android.os.Looper.loop
    MessageQueueThreadImpl.java:208 com.facebook.react.bridge.queue.MessageQueueThreadImpl$3.run
    Thread.java:841 java.lang.Thread.run

[jordanbyron]

Looks good to me. @huangmr thoughts?

[jordanbyron]

@AndrewJack @huangmr thanks fellas!