Disable Clerk access-review connector

Clerk's Backend API secret key only exposes the customer's application
end-users (GET /v1/users) -- the people who sign into the customer's
product -- not the Clerk workspace/dashboard team who administer the
platform. Those admins have no Backend API and are managed only in the
Clerk Dashboard UI. So an access-review campaign against Clerk reviews
the wrong population entirely (verified in prod: one source paginating
16K+ end-users), which is a compliance defect, not just the pagination
timeouts it also caused.

Unregister Clerk from the builtin provider registry and drop its driver,
provider registration, tests, and cassette so it can no longer be added
or fetched. Keep the ConnectorProviderClerk enum value, its IsValid
membership, the GraphQL enum value, and the frontend logo so existing
stored CLERK connectors still validate, serialize, and display (users
can still see and remove them). Drop it from ConnectorProviders so the
registry stays in sync with the registered set.

Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>

pkg/connector/provider/builtin.go

@@ -35,7 +35,6 @@ func NewBuiltinRegistry() *Registry {
 		bitbucketRegistration(),
 		brevoRegistration(),
 		brexRegistration(),
-		clerkRegistration(),
 		clickhouseRegistration(),
 		clickupRegistration(),
 		cloudflareRegistration(),