Update secure_coding_guidelines.md

doc/development/secure_coding_guidelines.md

@@ -544,7 +544,7 @@ This outputs `1` followed by the content of `/etc/passwd`.
 
 ### TLS minimum recommended version
 
-As we have [moved away from supporting TLS 1.0 and 1.1](https://about.gitlab.com/blog/2018/10/15/gitlab-to-deprecate-older-tls/), we should only use TLS 1.2 and above.
+As we have [moved away from supporting TLS 1.0 and 1.1](https://about.gitlab.com/blog/2018/10/15/gitlab-to-deprecate-older-tls/), you must use TLS 1.2 and above.
 
 #### Ciphers