[v7.0/forgejo] chore(security): update security.txt with new expiration date (#6669)

**Backport:** https://codeberg.org/forgejo/forgejo/pulls/6655

Same as https://forgejo.org/.well-known/security.txt

(cherry picked from commit 955f99b)

```
Conflicts:
	public/.well-known/security.txt
  trivial context conflict
```

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/6669
Reviewed-by: Gusted <[email protected]>
Co-authored-by: Earl Warren <[email protected]>
Co-committed-by: Earl Warren <[email protected]>

Author: earl-warren

public/.well-known/security.txt

@@ -5,4 +5,4 @@ Policy: https://codeberg.org/forgejo/forgejo/src/branch/forgejo/CONTRIBUTING.md
 Contact: mailto:[email protected]
 Encryption: https://keys.openpgp.org/vks/v1/by-fingerprint/1B638BDF10969D627926B8D9F585D0F99E1FB56F
 Preferred-Languages: en
-Expires: 2025-06-25T00:00:00Z
+Expires: 2026-07-16T23:59:59.000Z