http: use HTTP/1.1 as default in options builder

Author: itzg

src/main/java/me/itzg/helpers/http/SharedFetch.java

@@ -163,7 +163,7 @@ public static class Options {
         private final URI filesViaUrl;
 
         @Default
-        private final boolean useHttp2 = true;
+        private final boolean useHttp2 = false;
 
         private final boolean wiretap;