Fix Ember v4 deprecation warnings

[charlesfries]

• Bump ember-cli-fastboot and ember-test-selectors (fix Ember global warnings)
• Remove ember-keyboard-first-responder-inputs initializer
• Bump ember-modifier (fix modifier capability warning)

[lukemelia]

Thanks for working on this @charlesfries. It looks like this change may break Ember 3.8 (based on tests). I'm not opposed to doing that if it is necessary to support 4.0 cleanly, but we would need to do this as part of a breaking change.

[miguelcobain]

@charlesfries the initializer can be disabled in the config, but the deprecated imports are still there, so it seems like the deprecation is thrown anyway. Since we're doing a v7 anyway, we might as well remove it completely?

ember-modifier is compoatible with ember3.12+: https://github.com/ember-modifier/ember-modifier#compatibility

[lukemelia]

Closing in favor of @SergeAstapov's PRs linked above.