Fix internal property names

[andrewiggins]

I forgot to include the mangle.json pointer in the new package.json so some property names weren't being properly mangled.

Note: no tests fail because currently @preact/signals-react bundles the runtime package inside of it's bundled output and those properties are mangled - it doesn't import from /runtime. I left that as is for now since the /runtime package is intended to be an internal detail that will likely change in the future. I discovered this while working on the babel transform which does import from /runtime directly.

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🦋 Changeset detected

Latest commit: f8357cb4ebc69b438e507c6bedc5b42428a9f221

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

| Name | Type | | --------------------- | ----- | | @preact/signals-react | Patch |

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Size Change: -7 B (0%)

Total Size: 69.3 kB

Filename	Size	Change
docs/dist/assets/client.********.js	46.6 kB	+2 B (0%)
docs/dist/nesting-********.js	1.13 kB	-1 B (0%)
docs/dist/react-********.js	238 B	-1 B (0%)
packages/react/dist/signals.js	1.25 kB	-3 B (0%)
packages/react/dist/signals.mjs	1.2 kB	-4 B (0%)

ℹ️ View Unchanged

| Filename | Size | | :--- | :---: | | `docs/dist/assets/index.********.js` | 1.08 kB | | `docs/dist/assets/jsxRuntime.module.********.js` | 282 B | | `docs/dist/assets/preact.module.********.js` | 4 kB | | `docs/dist/assets/signals-core.module.********.js` | 1.42 kB | | `docs/dist/assets/signals.module.********.js` | 1.98 kB | | `docs/dist/assets/style.********.js` | 21 B | | `docs/dist/assets/style.********.css` | 1.21 kB | | `docs/dist/basic-********.js` | 244 B | | `docs/dist/demos-********.js` | 3.35 kB | | `packages/core/dist/signals-core.js` | 1.48 kB | | `packages/core/dist/signals-core.mjs` | 1.5 kB | | `packages/preact/dist/signals.js` | 1.21 kB | | `packages/preact/dist/signals.mjs` | 1.15 kB |

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