IntervalQueryBuilderTests#testNonIndexedFields test fix (elastic#40418)

This test checks that interval queries constructed against a field with no indexed
positions will throw exceptions. It uses a randomly-build IntervalsSourceProvider
against a fixed set of fields; however, the random source builder can occasionally
provide a source with a fixed field, meaning that even if the top-level query asks
for a set of intervals over a non-indexed field, the source will delegate to another
field, and no exception will be thrown.

This commit changes the test to always use a simple Match provider.

server/src/test/java/org/elasticsearch/index/query/IntervalQueryBuilderTests.java

@@ -294,7 +294,7 @@ public void testCombineDisjunctionInterval() throws IOException {
     }
 
     public void testNonIndexedFields() throws IOException {
-        IntervalsSourceProvider provider = createRandomSource();
+        IntervalsSourceProvider provider = new IntervalsSourceProvider.Match("test", 0, true, null, null, null);
         IntervalQueryBuilder b = new IntervalQueryBuilder("no_such_field", provider);
         assertThat(b.toQuery(createShardContext()), equalTo(new MatchNoDocsQuery()));