Minor javadoc updates (#108)

Author: hiranya911

src/main/java/com/google/firebase/auth/ListUsersPage.java

@@ -49,7 +49,7 @@ private ListUsersPage(
   }
 
   /**
-   * Checks if there is another page of users available for retrieving.
+   * Checks if there is another page of users available to retrieve.
    *
    * @return true if another page is available, or false otherwise.
    */

src/main/java/com/google/firebase/auth/UserRecord.java

@@ -172,8 +172,8 @@ public boolean isDisabled() {
   }
 
   /**
-   * Returns an array of UserInfo objects that represents the identities from different identity
-   * providers that are linked to this user.
+   * Returns an array of {@code UserInfo} objects that represents the identities from different
+   * identity providers that are linked to this user.
    *
    * @return an array of {@link UserInfo} instances, which may be empty.
    */