Administration: Rename the Site Editor menu item to "Edit Site"

[scruffian]

Renames the Appearance submenu item for the Site Editor from "Editor" to "Edit Site", so it matches the "Edit Site" node in the admin bar and the wording used elsewhere for the same action. Only the block theme branch is affected; the classic theme labels ("Design" and "Patterns") are unchanged. Note this modifies an existing translatable string, so it will need re-translation.

Trac ticket: https://core.trac.wordpress.org/ticket/66046

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 5
Used for: Locating the menu registration and making the one-line string change; reviewed by me.

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Props scruffian.

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