fix(docs): remove archived arduino/report-size-trends action

[Rotzbua]

Action not available anymore.

[per1234]

Despite the repository being archived, the arduino/report-size-trends action is still available for use in GitHub Actions workflows.

However, despite the action being created at their request, it turned out that in practice the developers never used the data it produced so it was determined to not be worth the effort to continue the maintenance of the project. So I do think it is a good idea to remove the mention of that action from this action's documentation.

Thanks @Rotzbua

[Rotzbua]

I think when a developer wants to analyze the data they feed it into their familiar metrics tool, since this action uses the very easily processable JSON format :)

Furthermore, the metric is only useful for application projects, since the total resource consumption is taken into account. For libraries it is unfortunately less useful. Because it is always considered the entire resource changes. Thus also includes changes by the Framework (Arduino/ESP) and not only those by the Library.