Fix to keep double quote of symbol in syntax higlight for crystal docs

[makenowjust]

crystal docs removes unneeded double of symbol. For example, there is src/hello.cr:

# ```
# :"hello"
# ```
module Hello
end

And crystal docs generates this against hello.cr:

But my expectation is this (and it is this PR's output):

I think it should keep user input even if this double quote is not needed.

[asterite]

Good catch, thanks!