ui: Update ember-{basic-dropdown,power-select} #4051

All 531 tests pass, 4 skipped in 7m 39s

535 tests ±0 531 ✔️ ±0 7m 39s ⏱️ +18s
    1 suites ±0     4 💤 ±0
    1 files ±0     0 ❌ ±0

Results for commit 6f0fc39. ± Comparison against earlier commit 7d0a450.