Two commands were formatted as quotes instead of code. This caused an issue where --branch was formatted with '–' instead of '--'. This caused an error when copying and pasting the command into a terminal:
```
[nix-shell:~/niv]$ niv modify nixpkgs –branch nixos-21.05
Invalid argument `–branch'
Usage: niv [-s|--sources-file FILE] [--no-colors] COMMAND
```