Bad paragraph example in tutorial

### Description

This has a heading inside of a `par`, which doesn't work anymore in 0.13.
```
#par(justify: true)[
  = Background
  In the case of glaciers, fluid
  dynamics principles can be used
  to understand how the movement
  and behaviour of the ice is
  influenced by factors such as
  temperature, pressure, and the
  presence of other fluids (such as
  water).
]
```