fix: update date and lastmod for CVPR 2026 presentations (#331)

## Background
The date and last modification date for the CVPR 2026 presentations were incorrectly set to an earlier date.

## Changes
- Updated `date` to 2026-02-21T00:00:00+00:00
- Updated `lastmod` to 2026-02-21T00:00:00+00:00

Author: shunk031

content/news/cvpr-2026-presentations/index.md

@@ -7,8 +7,8 @@ summary: ""
 authors: ["Shunsuke Kitada"]
 tags: ["News", "CVPR", "CVPR2026"]
 categories: ["News"]
-date: 2025-01-04T00:00:00+00:00
-lastmod: 2025-01-04T00:00:00+00:00
+date: 2026-02-21T00:00:00+00:00
+lastmod: 2026-02-21T00:00:00+00:00
 featured: false
 draft: false