fix: add @deprecated annotation to experimental.useCache (#92316)
### What?
Add a `@deprecated` JSDoc annotation to `experimental.useCache` in
`config-shared.ts`, pointing to `cacheComponents: true` as the
successor.
### Why?
`experimental.cacheComponents` already has `@deprecated use top-level
cacheComponents instead`, but `experimental.useCache` has no deprecation
notice despite `cacheComponents: true` being the documented successor.
This causes both developers and AI coding agents to use the old flag,
since nothing in the type definitions signals it's deprecated. IDEs and
agents rely on JSDoc annotations for guidance.
### How?
Replace the existing JSDoc comment on `experimental.useCache` with
`@deprecated use top-level cacheComponents instead`, matching the
existing pattern on `experimental.cacheComponents`.
## PR checklist (Fixing a bug)
- One-line JSDoc change, no tests needed
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