Update dependency ember-source to ~3.8.0

[renovate]

This PR contains the following updates:

Package	Type	Update	Change	References
ember-source	devDependencies	minor	~3.7.0 -> ~3.8.0	homepage, source

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Release Notes

emberjs/ember.js

v3.8.0

Compare Source

• #​17143 / #​17375 [FEATURE] Implement Element Modifier Manager RFC (see emberjs/rfcs#​0373).
• #​17054 / #​17376 [FEATURE] Implement array helper RFC (see emberjs/rfcs#​0318)
• #​16735 [BUGFIX] Observed properties not being marked as enum
• #​17498 [BUGFIX] Don't remove dep keys in didUnwatch
• #​17467 [BUGFIX] Fix substate interactions with aborts
• #​17413 [BUGFIX] Fix missing import in instance-initializer blueprint for ember-mocha
• #​17319 [CLEANUP] Remove deprecated 'POSITIONAL_PARAM_CONFLICT'
• #​17394 [CLEANUP] Remove deprecated code in mixins/array
• #​17244 / #​17499 Upgrade to Glimmer VM 0.37.1
  Fixes a few issues:
  • Usage of positional arguments with custom components.
  • Forwarding attributes via ...attributes to a dynamic component.
  • Prevent errors when rendering many template blocks (Error: Operand over 16-bits. Got 65536).
• #​17166 Improve performance of get() / set()
• #​16710 Deprecation of private NAME_KEY
• #​17216 Use native Error instead of custom Error subclass.
• #​17340 Remove unused hooks variable from qunit-rfc-232 util-test blueprint
• #​17357 Allow notifyPropertyChange to be imported from @​ember/object

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