fix: correctly iterate over plugins when using removePlugin

[Yukiniro]

Summary

When calling modifyConfig, if some plugins call removePlugin or addPlugin, the index of the plugin in this.#plugins will change. Since addPlugin uses push, it will not affect the index of other plugins. If it is removePlugin, it is necessary to consider whether the plugin to be removed is before the current traversal index. If so, the plugins after the index will move forward 1 in this.#plugins. If not, there will be no impact.

Related Issue

Closes #1487

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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[Timeless0911]

LGTM