Minor dashboard tweaks, fix flex-list margins (#26829)

Some small dashboard tweaks:

- Remove margin-bottom from divider so first item does not appear to
have un-equal margins
- Restore previous icon color
- Add slight margin-right to icon

Before:
<img width="783" alt="Screenshot 2023-08-31 at 00 10 28"
src="b75f70d7-8704-4afb-866d-fea0484c52d4">

After:
<img width="783" alt="Screenshot 2023-08-31 at 00 10 08"
src="50ed0c47-6f7c-449e-a054-13091369d43f">

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/shared/issuelist.tmpl

@@ -1,4 +1,4 @@
-<div id="issue-list" class="flex-list gt-pt-4">
+<div id="issue-list" class="flex-list">
 	{{$approvalCounts := .ApprovalCounts}}
 	{{range .Issues}}
 		<div class="flex-item flex-item-baseline">