The division operator `/` from Sass is deprecated because `/` is used in
CSS for uses other than dividing numbers. That's why we were getting
many warnings like:
```
Deprecation Warning: Using / for division outside of calc() is
deprecated and will be removed in Dart Sass 2.0.0.
Recommendation: math.div($line-height, 2) or calc($line-height / 2)
More info and automated migrator: https://sass-lang.com/d/slash-div
margin-top: $line-height / 2;
```
Since using math.div makes the code harder to read and `calc` is
universally supported by all browsers (although the implementation in
Internet Explorer doesn't work in certain cases), we're using `calc`
when assigning the value to a CSS property.
However, we're also using divisions when assigning Sass variables, and
in those cases using `calc` is trickier because sometimes these
variables are used in other operations. We'll handle these cases in the
next commit.
As mentioned in commit 925f04e3f, icon classes make screen readers
announce strange symbols and aren't properly displayed for people who
have changed their preferred font family.
We were using similar code in four different places; six, if we count
the welcome pages seeds. Reducing duplication in the pages seeds is a
bit tricky because administrators are supposed to edit their content and
might remove the HTML class we use to define styles. However, we can
share the code everywhere else.
Note that there's a bug in the application since we show that level 2
users cannot vote for budget projects but we give them permission to do
so in the abilities model. We're keeping the same behavior after this
refactoring but we might change it in the future.
