[shac] Fix a small typo in register.star.

The "formatter" property is set in the check itself, not in the
"shac.register_check" call.

Verified locally while migrating fuchsia-infra-bazel-rules to use
the shared repos.

Change-Id: I1d64af0aa83b7ae0bd5d036dd64c4e00a6ecd992
Reviewed-on: https://fuchsia-review.googlesource.com/c/shac-project/checks-cpp/+/1019513
Reviewed-by: Darren Chan <chandarren@google.com>
diff --git a/register.star b/register.star
index 64eecb5..672d03d 100644
--- a/register.star
+++ b/register.star
@@ -19,4 +19,4 @@
     #   emit_message: Message to print in case of a found issue.
     #     String. E.g. "Please run <> to format your code."
 
-    shac.register_check(clang_format.with_args(**kwargs), formatter = True)
+    shac.register_check(clang_format.with_args(**kwargs))