Fix due date rendering the wrong date in issue (#22302) (#22306)

Backport #22302

Previously, the last minute of the chosen date caused bad timezone
rendering.

For example, I chose January 4th, 2023.

### Before
```html
<time data-format="date" datetime="Wed, 04 Jan 2023 23:59:59 +0000">January 5, 2023</time>
```

### After
```html
<time data-format="date" datetime="2023-01-04">January 4, 2023</time>
```

---

Closes #21999

Signed-off-by: Yarden Shoham <hrsi88@gmail.com>

templates/repo/issue/view_content/sidebar.tmpl

@@ -413,7 +413,7 @@
 					<div class="df sb ac">
 						<div class="due-date tooltip {{if .Issue.IsOverdue}}text red{{end}}" {{if .Issue.IsOverdue}}data-content="{{.locale.Tr "repo.issues.due_date_overdue"}}"{{end}}>
 							{{svg "octicon-calendar" 16 "mr-3"}}
-							<time data-format="date" datetime="{{.Issue.DeadlineUnix.FormatLong}}">{{.Issue.DeadlineUnix.FormatDate}}</time>
+							<time data-format="date" datetime="{{.Issue.DeadlineUnix.FormatDate}}">{{.Issue.DeadlineUnix.FormatDate}}</time>
 						</div>
 						<div>
 							{{if and .HasIssuesOrPullsWritePermission (not .Repository.IsArchived)}}