chore(deps): update emqx/emqx docker tag to v5.8.2

[renovate]

This PR contains the following updates:

Package	Update	Change
emqx/emqx (source)	patch	5.8.1 -> 5.8.2

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Release Notes

emqx/emqx (emqx/emqx)

v5.8.2

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[fit2cloudrd]

这段代码的修改内容主要在以下几点：

1. emqx服务容器名称为${CONTAINER_NAME}, 在原有的基础上增加了一个别名。
2. 对于emqx服务镜像版本从3.x更改为4.x，最新版为“5.8.2”，此处是默认配置的更新。

由于没有具体问题需要分析和建议提供，请确保您提供的上下文清晰明确，在询问过程中描述清楚原始代码中存在的疑点或改进需求，以便给出有针对性的操作建议或调整说明。