[doc] Update README.md: experiemental => experimental #19179

Job	Run time
Check files	7s
Show Environment Variables	9s
Build and Test macos (CPU) (macos-10.15, 3.7, ON, cpu,vulkan)	21s
Build and Test (AMDGPU)	18s
Build and Test (manylinux2014)	9m 2s
Build and Test (GPU) (sm70, driver550)	19s
Build and Test (GPU) (sm70, driver510)	20s
Build and Test Windows (sm70)	45s
Check Static Analyzer	52s
Build and Test (GPU) (not sm70, driver550)	21s
AOT Build and Test Android Headless Demos	13s
Build and Test Windows (not sm70)	37s
Build and Test (GPU) (not sm70, driver510)	20s
AOT Build and Test Android Unity Examples	12s
AOT Build and Test (GPU) (self-hosted, cuda, vulkan, cn, driver550)	21s
Build and Test (Docs)	54s
Build and Test (Apple M1) (macos-latest, 3.8)	19s
Build iOS C-API Static Library	19s
AOT Build and Test Android Apps	14s
	16m 3s

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