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/frc971/control_loops/drivetrain/BUILD b/frc971/control_loops/drivetrain/BUILD
index 2e357c7..ed905cf 100644
--- a/frc971/control_loops/drivetrain/BUILD
+++ b/frc971/control_loops/drivetrain/BUILD
@@ -462,7 +462,7 @@
     srcs = [
         "drivetrain_lib_test.cc",
     ],
-    data = ["simulation_config.json"],
+    data = [":simulation_config"],
     defines =
         cpu_select({
             "amd64": [