Fix passing dynamic kwargs to where scope

When a hash passed along with kwargs, only the first statement
wins in Rails 6.1:

```ruby
Group.where({ created_at: 30.days.ago..2.days.ago }, id: 1)
```

Takes only the first argument into account.

In Rails 6.1 it should be passed as:

```ruby
Group.where(created_at: 30.days.ago..2.days.ago, id: 1)
```

That's why we need a splat operator here.

lib/gitlab/usage_data.rb

@@ -607,7 +607,7 @@ module Gitlab
           unique_users_all_imports: unique_users_all_imports(time_period),
           bulk_imports: {
             gitlab: DEPRECATED_VALUE,
-            gitlab_v1: count(::BulkImport.where(time_period, source_type: :gitlab))
+            gitlab_v1: count(::BulkImport.where(**time_period, source_type: :gitlab))
           },
           project_imports: project_imports(time_period),
           issue_imports: issue_imports(time_period),