fix: remove extra " typo in info.toml

[clairew]

When I run rustlings watch, main.rs panics when trying to read info.toml which is caused by the extra " character on line 748 in the info.toml file.

edit - realized we would want to keep "use std::fmt::Display;" so open to a better fix that the parser will be happy with

[elyscape]

This actually seems less like a typo and more of a failure to account for the way it's parsed.

The text immediately preceding the multi-line string delimiter is:

you may also need this: "use std::fmt::Display;"

This is followed by 3 double-quotes to close the multi-line string. Since there's nothing between the final double-quotes of the text and the string terminator, it gets parsed as the string ending and then having an extra double-quote immediately afterwards.

Looking at the rest of the file, probably the right answer here is to replace the double-quotes in the hint text with backticks, and also throw a trailing period after them.

[shadows-withal]

@all-contributors please add @clairew for content

[allcontributors[bot]]

@diannasoreil

I've put up a pull request to add @clairew! :tada: