Remove unnecessary use of `buildx` #1088

Job	Run time
Determine Python versions	6s
Build auto64 🎡 and source 📦 on Linux	20m 18s
Build 🎡 on windows-latest	8m 3s
Build aarch64 🎡 and source 📦 on Linux	32m 44s
Build 🎡 on macOS-12	5m 26s
Build 🎡 on macOS-14	3m 5s
Publish release 📦 to PyPI	0s
Publish development 📦 to TestPyPI	0s
	1h 9m 42s

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