Fix name of sysadmins group in GitLab

wiki/src/contribute/working_together/roles/sysadmins.mdwn

@@ -117,7 +117,7 @@ Git repositories.
 In order to get in touch with Tails sysadmins, you can:
 
 * Create an issue in the [[!tails_gitlab tails/sysadmin]] project
-* Ping all sysadmins anywhere in our [[!tails_gitlab desc="GitLab"]] by mentioning the `@sysadmins-team` group
+* Ping all sysadmins anywhere in our [[!tails_gitlab desc="GitLab"]] by mentioning the `@sysadmin-team` group
 * See if one of us is on shift in [[one of our chat rooms|about/contact#chat]]
 * Send an e-mail to [[the sysadmin's mailing list|about/contact#tails-sysadmins]]