Update dependency ember-source to v6.8.0

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
ember-source (source)	6.7.0 -> 6.8.0

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Release Notes

emberjs/ember.js (ember-source)

v6.8.0

Compare Source

• #​20950 / #​20961 / #​20963 [FEATURE] Upgrade glimmer-vm to build in Tracked Collections (previously provided by tracked-built-ins) per RFC #​1068.
  • [WARNING] Drops support for TS 5.0 and TS 5.1 under our TS Support policy
• #​20962 / #​20966 / #​20974 [FEATURE] Add renderComponent per RFC #​1099.
• #​20957 / #​20960 Add TS 5.8, 5.9 to the TS test matrix
• #​20988 [BUGFIX] Drop unnecessary package ember-cli-htmlbars-inline-precompile from component-test blueprint

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