Fix loading error

[dimkard]

On glossaico, when loading the spanish course, the following occurs: """ librelingo_yaml_loader.yaml_loader.ValidationError: There is an error with the schema at the following file path: [...]/spanish-from-english/course/activities/skills/continuous.yaml Original error message: "She's swimming in the sea" is not of type 'array'

Failed validating 'type' in schema['properties']['Phrases']['items']['properties']['Alternative translations']: {'items': {'type': 'string'}, 'type': 'array'}

On instance['Phrases'][6]['Alternative translations']: "She's swimming in the sea" """

This commit fixes the error

[dimkard]

@kantord ^^ :)

[kantord]

thank you! let me see