This way we make it easier to modify.
Note that, since the title of the page is "Administration" and it's in
the "Admin" section, we're adding an option to the `header` method in
order to avoid having a confusing title like "Administration - Admin".
Also note that, by removing the `title` HTML class, we avoid inheriting
styles from the `dashboard.scss` stylesheet, and now the heading is
displayed in the position it was meant to.
Finally, the concept of using a `main-class` for the current page comes
from a branch (currently in development) which will replace the <div>
tag with the `admin-content` class with a `main` tag.
We don't need to use `block_given?` since we specifically pass the block
parameter, particularly since we added the Style/ExplicitBlockArgument
rule in commit a102f3f0a.
When render the investment list component with the link "see all
investments", now we redirect to groups index page when a budget has
multiple headings.
