English grammar error in `Field that stores a per-document <code>long</code> values for scoring`

### Description

I don't think `a` and `values` can be used together.

Code link: https://github.com/apache/lucene/blob/1c655823dd85664b93a01c7ef3bd65fe094745fd/lucene/core/src/java/org/apache/lucene/document/SortedNumericDocValuesField.java#L24

Open lucene/core/src/java/org/apache/lucene/document/SortedNumericDocValuesField.java at the linked line and review the Javadoc for the per-document long values field. Correct the grammar so the article and plural wording agree, then verify that the documentation reads naturally and the change is limited to that sentence.

Written by the indexing model from the issue text.