Fix bug in usage of END_EXCLUDE (#679)

We use a [START_EXCLUDE silent] tag to exclude code from
snippets. This exclude block should end with an
[END_EXCLUDE] tag, instead of [END_EXCLUDE silent].

Co-authored-by: Ralston Da Silva <ralu@google.com>

Author: ralstondasilva

datastore/src/main/java/com/example/datastore/snippets/TimestampUpdateService.kt

@@ -34,7 +34,7 @@ class TimestampUpdateService : Service() {
 
     // [START_EXCLUDE silent]
     override fun onBind(intent: Intent): IBinder? = null
-    // [END_EXCLUDE silent]
+    // [END_EXCLUDE]
 
     override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
         serviceScope.launch {