[Doc] Examples are not displayed correctly in the REPL

```
help?> beam
search: beam break basename rem Real read real reim

DocStringExtensions.TypedMethodSignatures()

Defines the optimal control problem beam for a given back-end.

Arguments
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• model_backend::T: The modelling back-end, subtype of AbstractModelBackend.

• N::Int=0: Number of discretisation steps (optional).

Returns
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• Throws an ExtensionError if the required back-end is not available.

Example
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julia> beam(JuMPBackend(); N=20)
ERROR: ExtensionError(:JuMP)
```