Build instructions need updating

[hoheinzollern]

hierarchy-builder/README.md

Lines 92 to 100 in f4e4fda

	- You can install HB via OPAM
	```shell
	opam repo add coq-released https://coq.inria.fr/opam/released
	opam install coq-hierarchy-builder
	```
	- You can use it in nix with the attribute `coqPackages_8_XX.hierarchy-builder` e.g.
	via `nix-shell -p coq_8_13 -p coqPackages_8_13.hierarchy-builder`

Should be

 - You can install HB via OPAM 
  
 opam repo add rocq-released https://rocq-prover.org/opam/released
 opam install rocq-hierarchy-builder 
  
 - You can use it in nix with the attribute `rocqPackages_9_X.hierarchy-builder` e.g. 
   via `nix-shell -p rocq_9_0 -p rocqPackages_9_0.hierarchy-builder` 

(missing escaping due to markdown inside markdown)