Fix mdbook for web-docs.element.dev (#31350)

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

.github/workflows/docs.yml

@@ -49,7 +49,7 @@ jobs:
             - name: Setup mdBook
               uses: peaceiris/actions-mdbook@ee69d230fe19748b7abf22df32acaa93833fad08 # v2
               with:
-                  mdbook-version: "0.4.10"
+                  mdbook-version: "0.5.1"
 
             - name: Install mdbook extensions
               run: cargo install mdbook-combiner mdbook-mermaid

book.toml

@@ -4,7 +4,6 @@
 title = "Element Web & Desktop"
 authors = ["New Vector Ltd.", "The Matrix.org Foundation C.I.C."]
 language = "en"
-multilingual = false
 
 # The directory that documentation files are stored in
 src = "docs"