Improve display of Labels/Projects/Assignees sort options (#25886)

Labels:
Before: (no highlights)

![image](https://github.com/go-gitea/gitea/assets/18380374/88ffbff0-1b14-4d93-810d-f2ce2b2d7321)
After:

![image](https://github.com/go-gitea/gitea/assets/18380374/ab7b665b-d17c-4acd-a681-64cbb67ae460)

![image](https://github.com/go-gitea/gitea/assets/18380374/19f8a0d0-ad5f-4dbf-b45a-1001e60a8399)

Projects:
Before: (no highlights)

![image](https://github.com/go-gitea/gitea/assets/18380374/2079e6a8-8801-4662-acda-e248f115462f)

After:

![image](https://github.com/go-gitea/gitea/assets/18380374/7180a086-68be-49c4-bb29-3d05454fb41d)

![image](https://github.com/go-gitea/gitea/assets/18380374/3c5a791f-1852-4957-89b8-10940c672e10)

Assignee:
Before: (no highlights)

![image](https://github.com/go-gitea/gitea/assets/18380374/09273636-d9b1-4144-9533-2ce66cab8c49)
After:

![image](https://github.com/go-gitea/gitea/assets/18380374/24bd0cfe-b589-4c8a-be67-74f242dda6d3)

![image](https://github.com/go-gitea/gitea/assets/18380374/7476be73-5201-4330-82e2-44b0b5080f71)

options/locale/locale_en-US.ini

@@ -1384,7 +1384,7 @@ issues.delete_branch_at = `deleted branch <b>%s</b> %s`
 issues.filter_label = Label
 issues.filter_label_exclude = `Use <code>alt</code> + <code>click/enter</code> to exclude labels`
 issues.filter_label_no_select = All labels
-issues.filter_label_select_no_label = No Label
+issues.filter_label_select_no_label = No label
 issues.filter_milestone = Milestone
 issues.filter_milestone_all = All milestones
 issues.filter_milestone_none = No milestones