Update documentation regarding Merge actions

[SpenderJules]

Expected Behavior

In this web page: https://docs.mergify.com/actions/merge/ I expect to have the method replaced by merge_method following this changelog

Actual Behavior

method is present in the documentation

Steps to Reproduce the Problem

Website

Specifications

• Pull Request URL:
• Mergify Config URL:

[jd]

👋 @SpenderJules

We actually only renamed the queue action and not the merge action. In the queue action it seemed too confusing to have only method as the name.

OTOH it seemed quite clear that method in the merge action is the merge method.