message: doc: remove link to matlib4 for now.
diff: @@ -165,9 +165,11 @@ export class DocViewProvider implements Disposable {
  const books = {
  'Theorem Proving in Lean': 'https://leanprover.github.io/theorem_proving_in_lean4/',
  'Reference Manual': 'https://leanprover.github.io/lean4/doc/',
  - 'Mathematics in Lean': 'https://github.com/leanprover-community/mathlib4/',
  'Abbreviations cheat sheet': mkCommandUri('lean4.docView.showAllAbbreviations')
  };
  + // TODO: add mathlib4 when we have a book about it
  + // 'Mathematics in Lean': 'https://github.com/leanprover-community/mathlib4/',
  +
  for (const book of Object.getOwnPropertyNames(books)) {
  body.append($('<p>').append($('<a>').attr('href', books[book]).text(book)));
  }
  