Fix CrossClusterSearchLeakIT scroll size 0 (#78685)

The test would provoke a scroll of size 0, fixed to always use minimum
1 as size for scrolls.

Closes #78673

server/src/internalClusterTest/java/org/elasticsearch/search/ccs/CrossClusterSearchLeakIT.java

@@ -104,7 +104,7 @@ public void testSearch() throws Exception {
             searchRequest.allowPartialSearchResults(false);
             boolean scroll = randomBoolean();
             searchRequest.source(new SearchSourceBuilder().query(new MatchAllQueryBuilder())
-                .aggregation(terms("f").field("f").size(docs + between(scroll ? 1 : 0, 10))).size(between(0, 1000)));
+                .aggregation(terms("f").field("f").size(docs + between(0, 10))).size(between(scroll ? 1 : 0, 1000)));
             if (scroll) {
                 searchRequest.scroll("30s");
             }