thickness issue on page /content/applications/task03.html

Small issue - for a 3 mm disc it should be 3e-3 not 3e-4 in lines:
```python
import numpy as np

my_model.mesh = F.Mesh1D(vertices=np.linspace(0, 3e-4, num=1001))
```

it should be:
```python
import numpy as np

my_model.mesh = F.Mesh1D(vertices=np.linspace(0, 3e-3, num=1001))
```