Add cron schedule for 8 am CT & 1 pm CT, and exclude dependabot & tgonzalezorlandoarm #3712

Job	Run time
test-executorch-metal-build / macos-job	5m 6s
export-model-metal-artifact (openai, whisper-small, non-quantized) / macos-job	6m 57s
export-model-metal-artifact (mistralai, Voxtral-Mini-3B-2507, non-quantized) / macos-job	12m 11s
export-model-metal-artifact (openai, whisper-large-v3-turbo, non-quantized) / macos-job	7m 46s
test-model-metal-e2e (mistralai, Voxtral-Mini-3B-2507, non-quantized) / macos-job	7m 38s
test-model-metal-e2e (openai, whisper-small, non-quantized) / macos-job	5m 38s
test-model-metal-e2e (openai, whisper-large-v3-turbo, non-quantized) / macos-job	5m 51s
	51m 7s

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