rust: macros: indent list item in `module!`'s docs

Like commit e516211f ("rust: macros: indent list item in `paste!`'s
docs"), but for `module!`.
Reviewed-by: Trevor Gross <tmgross@umich.edu>
Link: https://lore.kernel.org/r/20240725184644.135185-1-ojeda@kernel.orgSigned-off-by: Miguel Ojeda <ojeda@kernel.org>