Fix Using Context section

[vzakaznikov]

Fix https://testflows.com/handbook/#Using-Contexts section. Invalid syntax and wording.

The main use case for using context is to avoid passing along common arguments to sub-tests, and becuase contexts enable them to pass_automatically_.

[Selfeer]

The main use case for using context is to avoid passing along common arguments to sub-tests, and becuase contexts enable > them to pass_automatically_.

becuase - should be changed to because
contexts - the s should probably also be inside `` as contexts