fix wording in SECURITY.md (go-gitea#27463)

Author: Nuyube

SECURITY.md

@@ -12,7 +12,7 @@ Please **DO NOT** file a public issue, instead send your report privately to `se
 
 ## Protecting Security Information
 
-Due to the sensitive nature of security information, you can use below GPG public key encrypt your mail body.
+Due to the sensitive nature of security information, you can use the below GPG public key to encrypt your mail body.
 
 The PGP key is valid until June 24, 2024.