Enable sdpa backends for server export in export.py #2466

Job	Run time
test-advanced-mps-macos / macos-job	7m 12s
test-evaluation-mps-macos / macos-job	7m 53s
test-gguf-mps-macos / macos-job	7m 10s
test-multimodal-mps-macos / macos-job	42s
test-native-mps-macos / macos-job	4m 22s
test-quantization-mps-macos / macos-job	39m 46s
test-readme-mps-macos / macos-job	1m 54s
	1h 8m 59s

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