Specify build target arguments (or not) consistently in docs

[cfr42]

For check we have

$ l3build check ⟨name(s) ⟩

Similar syntax is used for save, tag and upload.

For doc we have

$ l3build doc

The explanation does imply <name(s)> can be given, since it says what happens if none are specified. But this is not great for quickly checking whether arguments are allowed here, so I'd personally prefer the first syntax to the second, but consistent use of either would be less confusing since it would be obvious you had to scan through the text in that case.

[josephwright]

Where are you looking? In the docs, we have l3build check then l3build check <names>, and l3build doc followed by l3build doc <names>, etc.

[cfr42]

Where are you looking?

I'm really, really sorry.