Remove most HTML/CSS/JS assets from the backend service WAR

It only needs the error page HTML files; everything else isn't used by endpoints
served by the backend service and only serves to increase build times
(especially compiling all that JS).

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=202229514

java/google/registry/BUILD

@@ -133,7 +133,7 @@ zip_file(
     },
     deps = [
         ":common_war",
-        "//java/google/registry/ui:war",
+        "//java/google/registry/ui:minimal_war",
     ],
 )