Indentation fix of code block in docs/user-guide/sni.md
Indentation fix of code block in docs/user-guide/sni.md

A certain code block was not indented properly, which caused the sintax highlighter to not work. See: https://www.getambassador.io/user-guide/sni/

datawire/ambassador,datawire/ambassador,datawire/ambassador,datawire/ambassador,datawire/ambassador