Add UI polish to issue analytics table

What does this MR do and why?

On the Issue analytics page, the MR adds padding between the to the first 2 lines of text in the first table cell and removes the alternating rows stripes, making the table visually consistent with tables found under the "Analyze" parent. This change aligns with the spacing guidelines in Pajamas.

Related KR: https://gitlab.com/gitlab-com/gitlab-OKRs/-/work_items/4493+

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