Update README.md

[geomat0101]

existing advice is broken, results in 'bash: /etc/apt/sources.list.d/httpie.list: Permission denied' because it is trying to redirect the output of the sudo command outside privileged context.

Converted it to a subshell invocation

[mikelolasagasti]

There's an alternative way to achieve the same result that I find more concise and readable. Instead of using the sudo sh -c approach, you could consider the following:

echo "deb [arch=amd64 signed-by=/usr/share/keyrings/httpie.gpg] https://packages.httpie.io/deb ./" |sudo tee -a /etc/apt/sources.list.d/httpie.list

[jkbrzt]

Fixed via #1557. Thanks!