Fix query size for query_lookup to return more than 10 documents (opensearch-project#5807)

Signed-off-by: Taylor Gray <tylgry@amazon.com>
Signed-off-by: Jonah Calvo <caljonah@amazon.com>

Author: graytaylor0

data-prepper-plugins/opensearch/src/main/java/org/opensearch/dataprepper/plugins/sink/opensearch/index/ExistingDocumentQueryManager.java

@@ -172,6 +172,7 @@ private MsearchRequest buildMultiSearchRequest() {
                 m.searches(s -> s
                         .header(h -> h.index(index))
                         .body(b -> b
+                                .size(values.size())
                                 .source(source -> source.filter(f -> f.includes(queryTerm)))
                                 .query(Query.of(q -> q
                                         .terms(TermsQuery.of(t -> t