Code Insights: Remove data series name field for compute powered series

Created by: vovakulikov

Follow up for https://github.com/sourcegraph/sourcegraph/pull/40038

Since we don't support multiseries for compute powered insight we don't need to ask users to fill out series name field.

From @AlicjaSuska (https://github.com/sourcegraph/sourcegraph/pull/40038#pullrequestreview-1065102658)

I'm not sure about how useful is to keep both 'name' for the series and 'name' for the chart. In this case when we only have one series, they would probably be the same in most cases. My proposition is to remove the 'name' field form the data series form for now. Also, data series name is not displayed in the final chart on the dashboard.

/cc @joelkw @felixfbecker @vovakulikov @unclejustin