Hyphenate PEM encoded

Author: Brad Sevy

doc/settings/ssl/ssl_troubleshooting.md

@@ -117,7 +117,7 @@ the message "Skipping `cert.pem`" after running `gitlab-ctl reconfigure`, that
 means there may be one of four issues:
 
 1. The file in `/etc/gitlab/trusted-certs/` is a symlink
-1. The file is not a valid PEM or DER-encoded certificate
+1. The file is not a valid PEM- or DER-encoded certificate
 1. Perl is not installed on the operating system which is needed for c_rehash to properly symlink certificates
 1. The certificate contains the string `TRUSTED`