feat(crons): Update onboarding empty state illustration

Add a new crons-specific cuckoo clock illustration for the crons
onboarding empty states, replacing the generic onboarding-preview SVG
in cron views.

Author: evanpurkhiser

static/app/views/detectors/list/cron.tsx

@@ -2,7 +2,7 @@ import {useMemo, useRef} from 'react';
 import styled from '@emotion/styled';
 import {PlatformIcon} from 'platformicons';
 
-import onboardingImg from 'sentry-images/spot/onboarding-preview.svg';
+import onboardingImg from 'sentry-images/spot/crons-onboarding.svg';
 
 import {LinkButton} from '@sentry/scraps/button';
 import {Flex, Stack} from '@sentry/scraps/layout';

static/app/views/insights/crons/components/platformPickerPanel.tsx

@@ -1,7 +1,7 @@
 import styled from '@emotion/styled';
 import {PlatformIcon} from 'platformicons';
 
-import onboardingImg from 'sentry-images/spot/onboarding-preview.svg';
+import onboardingImg from 'sentry-images/spot/crons-onboarding.svg';
 
 import {Button} from '@sentry/scraps/button';
 import {Flex} from '@sentry/scraps/layout';