Depend on config rule instead of file.

The aos_config rule used to require you to depend on {name}.json to get
the output.  That was weird and hid private/testonly/etc.  Instead,
depend on the rule directly.

Change-Id: I1596a6c1f44b246a0db1bbc562468530a0b69614
diff --git a/y2020/BUILD b/y2020/BUILD
index cd977f9..2d3f0e5 100644
--- a/y2020/BUILD
+++ b/y2020/BUILD
@@ -9,7 +9,7 @@
         ":setpoint_setter",
     ],
     data = [
-        ":config.json",
+        ":config",
     ],
     start_binaries = [
         "//aos/events/logging:logger_main",
@@ -29,7 +29,7 @@
         "//y2020/vision:viewer",
     ],
     data = [
-        ":config.json",
+        ":config",
     ],
     dirs = [
         "//y2020/www:www_files",
@@ -218,7 +218,7 @@
     name = "web_proxy",
     srcs = ["web_proxy.sh"],
     data = [
-        ":config.json",
+        ":config",
         "//aos/network:web_proxy_main",
         "//y2020/www:camera_main_bundle",
         "//y2020/www:field_main_bundle",