MM-51763 Use STRIPE_PUBLIC_KEY from webpack (monorepo) (#22774)

* use webpack build time stripe public key

webapp/channels/src/components/payment_form/stripe.ts

@@ -25,4 +25,5 @@ function devConfirmCardSetup(confirmCardSetup: ConfirmCardSetupType): ConfirmCar
 export const getConfirmCardSetup = (isDevMode?: boolean) => (isDevMode ? devConfirmCardSetup : prodConfirmCardSetup);
 
 export const STRIPE_CSS_SRC = 'https://fonts.googleapis.com/css?family=Open+Sans:400,400i,600,600i&display=swap';
-export const STRIPE_PUBLIC_KEY = 'pk_test_ttEpW6dCHksKyfAFzh6MvgBj';
+//eslint-disable-next-line no-process-env
+export const STRIPE_PUBLIC_KEY = process.env.STRIPE_PUBLIC_KEY || 'pk_test_ttEpW6dCHksKyfAFzh6MvgBj';