ssl-observatory.dtd spelling error

The line:

<!ENTITY ssl-observatory.warning.text "EFF's SSL Observatory has issued a warning about the HTTPS certificiate(s) for this site:">

should read

<!ENTITY ssl-observatory.warning.text "EFF's SSL Observatory has issued a warning about the HTTPS certificates(s) for this site:">

https://raw.githubusercontent.com/EFForg/https-everywhere/master/src/chrome/locale/en/ssl-observatory.dtd