doc: fix invalid Commands.md example for introspect [skip ci]
It requires at least one option argument, and the one that provides
"basic information" about the project is --projectinfo, so let's use
that to demo the command.
Fixes
@@ -151,7 +151,7 @@ Displays information about a configured meson project.
Display basic information about a configured project in `builddir`:
```
-meson introspect builddir
+meson introspect builddir --projectinfo
```
### install
