tree(fix): Remove accidentally exposed identifier API

[noencke]

Description

This is a patch of PR 20718

This bug fix removes an accidentally-exposed API in tree. The API in question, identifiers, is exposed in schema creation but is not usable in the current state and thus this change will not have any customer impact. The API will be re-added in the future when it functions.

[msfluid-bot]

⯆ @fluid-example/bundle-size-tests: -594 Bytes

Metric Name	Baseline Size	Compare Size	Size Diff
aqueduct.js	452.28 KB	452.28 KB	■ No change
azureClient.js	545.36 KB	545.36 KB	■ No change
connectionState.js	680 Bytes	680 Bytes	■ No change
containerRuntime.js	255.17 KB	255.17 KB	■ No change
fluidFramework.js	339.68 KB	339.39 KB	⯆ -297 Bytes
loader.js	129.89 KB	129.89 KB	■ No change
map.js	41.35 KB	41.35 KB	■ No change
matrix.js	143.62 KB	143.62 KB	■ No change
odspClient.js	513.35 KB	513.35 KB	■ No change
odspDriver.js	97.06 KB	97.06 KB	■ No change
odspPrefetchSnapshot.js	41.93 KB	41.93 KB	■ No change
sharedString.js	161.39 KB	161.39 KB	■ No change
sharedTree.js	339.68 KB	339.39 KB	⯆ -297 Bytes
Total Size	3.14 MB	3.14 MB	⯆ -594 Bytes

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Baseline commit: b2bbc67

Generated by 🚫 dangerJS against 9b18de1

[tylerbutler]

Please add more details to the PR description, and perhaps a more descriptive title, before merge. Since this will go out as a patch the info here will be what winds up in the release notes, so make it as customer-ready as possible.