Fix broken link to module specifier section

[sodic]

The docs update for TypeScript 5.8 (#3345) changed the chapter title without updating the references:

• "Module specifiers are not transformed" was changed to "Module specifiers are not transformed by default"
• Markdown continued linking to #module-specifiers-are-not-transoformed

This change broke two links in the document, and this PR fixes them. I ran the website and tested the links locally, everything looks OK.

Thanks for the great guide on the module craziness, very helpful!