Update Wear SDK tag reference in building doc (4.4W > 4.4W2).

Author: eyecatchup

doc/BUILDING.md

@@ -49,7 +49,7 @@ This is a Gradle-based project that works best with [Android Studio].
        - Tools > Android SDK Tools (rev 23.0.5 or above)
        - Tools > Android SDK Build-tools version 20
        - Tools > Android SDK Build-tools version 21 (rev 21.0.2 or above)
-       - Android 4.4W > SDK Platform (API 20)
+       - Android 4.4W2 > SDK Platform (API 20)
        - Android 5.0 > SDK Platform (API 21)
        - Extras > Android Support Repository
        - Extras > Android Support Library