Refer to Datastore everywhere correctly by its capitalized form

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=147479683

java/google/registry/util/CollectionUtils.java

@@ -113,7 +113,7 @@ public class CollectionUtils {
    * Turns an empty collection into a null collection.
    *
    * <p>This is unwise in the general case (nulls are bad; empties are good) but occasionally needed
-   * to cause JAXB not to emit a field, or to avoid saving something to datastore. The method name
+   * to cause JAXB not to emit a field, or to avoid saving something to Datastore. The method name
    * includes "force" to indicate that you should think twice before using it.
    */
   @Nullable