Kotlin lexer counts enclosing backtick as an error syntax

[notdryft]

Backticked methods as such:

http("My Request").get("myUrl").check(status().`is`(200))

Renders as:

I found that in the following line of code there is an opening backtick but not a closing one: https://github.com/alecthomas/chroma/blob/master/lexers/k/kotlin.go#L21