style(l10n): simplify update button text in mod management header

[3gf8jv4dv]

English and Spanish only.

Reduces clutter by simplifying the text, resulting in a cleaner UI.

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承接 #4711。

「Check for Updates」还是略长。本 PR 简化为「Update」以进一步精简 UI。

以下是英语 UI 效果：

配合 #4711 时的西班牙语效果：

[Copilot]

Pull Request Overview

This PR simplifies the update button text in the mod management header by shortening "Check for Updates" to "Update" and "Comprobar actualizaciones" to "Actualizar" in English and Spanish localizations respectively, creating a cleaner and less cluttered UI.

• Simplified English button text from "Check for Updates" to "Update"
• Simplified Spanish button text from "Comprobar actualizaciones" to "Actualizar"

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
I18N.properties	Updated English localization key mods.check_updates with simplified button text
I18N_es.properties	Updated Spanish localization key mods.check_updates with simplified button text

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