Replace redis-sidekiq shard template to use the generic shard template

In gitlab-com/runbooks!8781 (merged), we added a generic shard template which can be used for any services with shard level monitoring enabled.

This is to refactor redis-sidekiq to use that shard template instead of redisShard https://gitlab.com/gitlab-com/runbooks/-/blob/ba224dff27a453fc8970ec3c6c339eaa24e9ee68/libsonnet/gitlab-dashboards/redis_common_graphs.libsonnet#L570.