fix(phosphor-icon): remove org-scoped app installations query [EXT-7458]

[Jared Jolton (jjolton-contentful)]

Summary

• Removes expensive org-scoped CMA calls from the phosphor-icon Field component that were contributing to elevated 429 rates (INC-1276)
• The fetchLatestInstallationParameters callback previously called appInstallation.getForOrganization() on mount AND on every dialog open — two org-scoped calls per user interaction
• Replaced with a synchronous read of sdk.parameters.installation which already contains the correct parameters without any network overhead

Context

This is part of the broader effort in EXT-7458 to eliminate unnecessary org-scoped appInstallation.getForOrganization queries across marketplace apps. These calls are expensive, hit rate limits, and the SDK already provides the installation parameters synchronously.

Changes

• apps/phosphor-icon/src/locations/Field.tsx — removed fetchLatestInstallationParameters async callback and the useEffect that synced params on mount; replaced with a simple synchronous getInstallationParameters helper that reads from sdk.parameters.installation
• apps/phosphor-icon/src/locations/Field.spec.tsx — updated tests to reflect that params now come directly from the SDK rather than a CMA fetch

Test plan

• All 37 existing tests pass (npm test in apps/phosphor-icon)
• Verify in staging that the icon picker dialog still opens with correct weights/positions/allowed icons
• Confirm no org-scoped CMA calls in network tab when loading the field or opening the dialog

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