gh-92417: `asyncio` docs: `asyncio.run()` is available on all supported Python versions (GH-92419)

(cherry picked from commit f4e317b3)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

Doc/library/asyncio.rst

@@ -17,7 +17,6 @@
            await asyncio.sleep(1)
            print('... World!')
 
-       # Python 3.7+
        asyncio.run(main())
 
 asyncio is a library to write **concurrent** code using