Advance RFC #0743 `"EmberData | Deprecate Legacy Imports"` to Stage Released #739

Job	Run time
Does PR add RFCs?	9s
Only one RFC can be added in a PR	0s
RFC must be in only one stage before merging (labels)	0s
Stage must be 'Exploring' (via label) for new RFC before merging	0s
Verify Accepted PR URL is correct	0s
Filename matches RFC number	0s
Frontmatter stage must be 'accepted' before merging	0s
	9s

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