Revert changes to build.gradle from change f15005cb

Reverting build.gradle in change f15005cb84eb590af60359d3504d548bcc7734dc
to fix the sample-create script.

Change-Id: I8fd049ab7fef3a8599e7abd11c5f5ac6d1ed2811
diff --git a/build.gradle b/build.gradle
index 2dd7189..c7e6753 100644
--- a/build.gradle
+++ b/build.gradle
@@ -14,6 +14,9 @@
 * limitations under the License.
 */
 
+// The SampleGenPlugin source is in the buildSrc directory.
+import com.example.android.samples.build.SampleGenPlugin
+apply plugin: SampleGenPlugin
 
 // Add a preflight task that depends on the "refresh" task that gets
 // added by the SampleGenPlugin.