Update `CreatePoll` to use `u16` for duration (#3433) #6387

Job	Run time
Check minimal versions	1m 1s
Build docs	51s
Examples	4m 14s
Test (macOS)	3m 8s
MSRV	1m 9s
Test (nightly)	2m 14s
Test (beta)	2m 11s
Test (no default features)	57s
Test (stable)	2m 17s
Test (no cache)	2m 2s
Test (no gateway)	1m 30s
Test (simd-json)	2m 5s
Test (unstable API + typesize, default unstable_discord_api typesize, true)	1m 15s
Test (native-tls)	1m 45s
Test (builder without model, builder, true)	46s
Test (Windows)	6m 20s
Test (unstable Discord API (no default features), unstable_discord_api, true)	41s
Test (chrono, chrono)	57s
Test (unstable Discord API features)	2m 8s
	37m 31s

Provide feedback