assert we only support Float queries

Author: iverase

server/src/main/java/org/elasticsearch/search/vectors/AbstractIVFKnnVectorQuery.java

@@ -124,6 +124,7 @@ public Query rewrite(IndexSearcher indexSearcher) throws IOException {
         TaskExecutor taskExecutor = indexSearcher.getTaskExecutor();
         List<LeafReaderContext> leafReaderContexts = reader.leaves();
 
+        assert this instanceof IVFKnnFloatVectorQuery;
         int totalVectors = 0;
         for (LeafReaderContext leafReaderContext : leafReaderContexts) {
             LeafReader leafReader = leafReaderContext.reader();