[doc] Improve V7 migration guide regarding hook "After" result

[fmagaldea]

Hi,

During the migration of my project from V6 to V7, I found at least 2 breaking changes in the hook "After".

Considering the code

After(async function(scenario) {
 ...
});

, then I detected the following 2 changes:

• V6 scenario.result.retried > in V7 this boolean was renamed to scenario.result.willBeRetried
• V6 scenario.result.status was previously a string, which value could be for example failed > in V7 is now a number, whose all possible values can be found in object Status that can be imported from cucumber const {Status} = require('@cucumber/cucumber');

It would be nice to have a more clear overview of all changes in this objects.

Anyway thanks for this great tool!