Fixed check for emoji index

The emoji *must* be at index=2 as each line looks like:
    "* <commit message>"
We use index=2 to make test whether emoji is first character(s) in the
commit message

ghost/release-utils/lib/utils.js

@@ -18,7 +18,7 @@ module.exports.filterEmojiCommits = (content) => {
         obj[index] = line;
 
         const match = emojiRegex().exec(line);
-        return match && match.index !== 2;
+        return match && match.index === 2;
     });
 
     return content;