Update documentation of 'inspect' command with '--raw' attribute

[jgsogo]

Docs for conan-io/conan#4903

[solvingj]

I think the example should be:
$ conan inspect zlib/1.2.11@conan/stable -a settings --raw

[jgsogo]

No, --raw expects one argument. You can read about the reasoning here. The problem was that some attributes expands over more than one line (options, default_options) and it could be hard to know which lines correspond to which attributes. So, one attribute at a time is the easiest way to know that all lines correspond to that attribute.