docs(codex): update install command to use openai-curated marketplace

[evanpurkhiser]

No description provided.

[sentry]

Bug: The updated installation command codex plugin add sentry@openai-curated in the README is likely incorrect, as the plugin's marketplace configuration still points to sentry-plugin-marketplace.
_{Severity: MEDIUM}

Suggested Fix

Either update the README.md to use the correct, existing installation command referencing sentry-plugin-marketplace, or update the project's configuration and CI/CD pipeline to properly publish the plugin to the openai-curated marketplace to match the new documentation.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: plugin-src/codex/README.md#L16-L18

Potential issue: The `README.md` for the Codex plugin was updated with a new
installation command: `codex plugin add sentry@openai-curated`. However, the plugin's
configuration in `plugin-src/codex/marketplace.json` still defines the marketplace as
`sentry-plugin-marketplace`. There is no evidence in the repository that the plugin is
configured, built, or published to an `openai-curated` marketplace. Users following the
new instructions will likely encounter an error because the plugin is not available from
the specified marketplace, making the documentation misleading and the installation
process non-functional.

_{Did we get this right? 👍 / 👎 to inform future reviews.}