fix link

Author: sebasti810

doc/bash.sh

@@ -6,7 +6,7 @@ curl -Lo mdbook.tar.gz https://github.com/rust-lang/mdBook/releases/download/v0.
 tar -xvzf mdbook.tar.gz
 
 # load katex and unpack it
-curl -Lo mdbook-katex.tar.gz https://github.com/lzanini/mdbook-katex/releases/download/v0.2.13/mdbook-katex-v0.2.13-x86_64-unknown-linux-musl.tar.gz
+curl -Lo mdbook-katex.tar.gz https://github.com/lzanini/mdbook-katex/releases/download/0.9.0-binaries/mdbook-katex-v0.9.0-x86_64-unknown-linux-gnu.tar.gz
 tar -xvzf mdbook-katex.tar.gz
 
 chmod +x mdbook mdbook-katex