Not working with WordPress >=6.6

ref: #254

After updating to WordPress 6.6, the Isolated Block Editor is not working. Error in the console:

```
Uncaught Error: You tried to opt-in to unstable APIs without confirming you know the consequences. This feature is only for JavaScript modules shipped with WordPress core. Please do not use it in plugins and themes as the unstable APIs will removed without a warning. If you ignore this error and depend on unstable features, your product will inevitably break on the next WordPress release.
at __dangerousOptInToUnstableAPIsOnlyForCoreModules (private-apis.js?ver=53100b466d825a8b9022:115:11)
at ../../../node_modules/.pnpm/@automattic+isolated-block-editor@2.29.0_@babel+helper-module-imports@7.24.7_@babel+types@7.2_4lglvpqjpsedbgvkrr4wlluyyq/node_modules/@automattic/isolated-block-editor/build-module/components/block-editor/unlock.js (unlock.js:7:53)
at __webpack_require__ (chunk loaded:30:1)
at ../../../node_modules/.pnpm/@automattic+isolated-block-editor@2.29.0_@babel+helper-module-imports@7.24.7_@babel+types@7.2_4lglvpqjpsedbgvkrr4wlluyyq/node_modules/@automattic/isolated-block-editor/build-module/components/block-editor/sidebar-heading.js (post-text-editor.js:114:1)
at __webpack_require__ (chunk loaded:30:1)
at ../../../node_modules/.pnpm/@automattic+isolated-block-editor@2.29.0_@babel+helper-module-imports@7.24.7_@babel+types@7.2_4lglvpqjpsedbgvkrr4wlluyyq/node_modules/@automattic/isolated-block-editor/build-module/components/block-editor/sidebar.js (sidebar-heading.js:41:1)
at __webpack_require__ (chunk loaded:30:1)
at ../../../node_modules/.pnpm/@automattic+isolated-block-editor@2.29.0_@babel+helper-module-imports@7.24.7_@babel+types@7.2_4lglvpqjpsedbgvkrr4wlluyyq/node_modules/@automattic/isolated-block-editor/build-module/components/block-editor/index.js (footer.js:44:1)
at __webpack_require__ (chunk loaded:30:1)
at ../../../node_modules/.pnpm/@automattic+isolated-block-editor@2.29.0_@babel+helper-module-imports@7.24.7_@babel+types@7.2_4lglvpqjpsedbgvkrr4wlluyyq/node_modules/@automattic/isolated-block-editor/build-module/components/block-editor-contents/index.js (editor-content.js:45:1)
```

Opt-in string was changed in https://github.com/WordPress/gutenberg/pull/62635, so ISO Editor also needs to update it

Start with the isolated-block-editor unlock.js entry point shown in the console and compare its unstable API opt-in with the change in Gutenberg pull request 62635. Reproduce the failure with WordPress 6.6 or later, then verify that the Isolated Block Editor loads without the console error.

Written by the indexing model from the issue text.