Fix the icon warnings in the tests

[steffenkleinle]

Describe the Bug

Since the migration to the new design system and to react-native-paper, we have lots of warnings in our tests. These should be investigated and fixed. An example is e.g. the test at native/src/components/__tests__/Caption.spec.tsx.

Steps to Reproduce

1. Execute the test(s)
2. See the warnings in the console

Expected Behavior

No warnings

Related Issues

N/A

Additional Information

Example warning:

  console.warn
    Tried to use the icon 'checkbox-blank-outline' in a component from 'react-native-paper', but none of the required icon libraries are installed. To fix this, please install one of the following:
    - @expo/vector-icons
    - @react-native-vector-icons/material-design-icons
    - react-native-vector-icons
    
    You can also use another method to specify icon: https://callstack.github.io/react-native-paper/docs/guides/icons