Fix dialogs in ProjectExplorerPlugin::buildQueueFinished().

Use ICore::dialogParent(), fix capitalization, remove exclamation
mark and trailing newline.

Change-Id: Ia9b28aeb95e2047595173b41fc69dcf6326e0f1f
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>