Garnissez vos yeux d’émerveillement... vivez comme si vous deviez mourir dans dix secondes. Voyez le monde. Il est plus fantastique que tous les rêves fabriqués ou payés dans les usines.
We traced this quote to a primary published source and confirmed the words are genuinely the author's. You can cite it with confidence.
The wording that circulates online typically drops the dialogue tag and the closing two sentences, condensing the passage to "Stuff your eyes with wonder, live as if you'd drop dead in ten seconds." This shortened form is a faithful compression rather than an alteration, but it is not the text as published.
Attribution to Bradbury is correct in the authorial sense: he wrote the passage. The sentiment is voiced by a character recalling another character, which is worth noting for readers who encounter the line presented as Bradbury speaking in his own voice.