Convert inline code references to use double backticks in the standard library

[tothambrus11]

We have already converted the standard library to use our new syntax for special sections inside https://github.com/hylo-lang/hylodoc/tree/dev/Sources/StandardLibrary/Sources

Hylo code references are still not updated though, so there are still places where `myFunction(_:)` is written instead of ``myFunction(_:)``.

Updating the standard library to use this syntax would make the references be checked when generating the documentation, so it would be harder to accidentally making documentation obsolete when doing some refactoring.

For the details of the syntax, see https://github.com/hylo-lang/hylodoc/blob/dev/SyntaxReference.md#symbol-references