[poetry-club-door-policy] Template string delimiters

Hiya !

The exemplar suggests using interpolating delimiters, which seems awry :

I’m suggesting a change to

exercises/concept/poetry-club-door-policy/.meta/exemplar.js

of :

- return frontDoorPassword(word) + `, please`;
+ return frontDoorPassword(word) + ", please";

Oh yeah, that’s a mistake. Feel free to PR!

Either that change or:

- return frontDoorPassword(word) + `, please`;
+ return `${frontDoorPassword(word)}, please`;

Both are equally idiomatic.