Using props m, p, mx, my, marginBottom etc. on <Text />, <Heading /> doesn't have any effect

### Describe Your Environment

What version of Spectacle are you using? (can be found by running `npm list spectacle`)

```
spectacle@6.0.2
```

What version of React are you using? (can be found by running `npm list react`)

```
react@16.13.1
```

What browser are you using?

```
chrome
```

What machine are you on?

```
macOS / macbook pro
```

### Describe the Problem

https://codesandbox.io/s/simple-spectacle-example-ztd4b?file=/src/index.js

Using props `m`, `mx`, `my`, `p`, `px`, `py` doesn't work for `` and ``.

See generated CSS

**Expected behavior:**

It should change `padding` and `margin`.

**Actual behavior:**

`padding` and `margin` doesn't change or rules are overriden.

### Additional Information

N/A