Remove pre-SDK 15 code in ReactAppManager (#1646)
Remove pre-SDK 15 code in ReactAppManager (#1646)

We include only SDK 17+ and the version manager for those versions all implement the selectors we were testing for.

Test Plan: Search for `devMenuItemsForBridge` and `selectDevMenuItemWithKey` and make sure all the included version managers implement those selectors. Launch a test app and ensure that the dev menu doesn't break when displayed or used.

fbshipit-source-id: 50f8820

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