add comment about cast #946

Job	Run time
android	20m 2s
docs	54s
air-samples (4.0.5)	2m 35s
flash-samples	46s
air-samples (4.1.5)	2m 35s
air-samples (4.2.5)	2m 57s
html5-samples	1m 13s
ios	17m 32s
air-samples (4.3.1)	2m 38s
linux	11m 39s
macos	19m 4s
windows	10m 35s
package-haxelib	9m 23s
hashlink-samples (windows-latest)	1m 53s
neko-samples (3.4.7, windows-latest)	1m 48s
hashlink-samples (ubuntu-20.04)	1m 2s
neko-samples (3.4.7, ubuntu-20.04)	3m 3s
hashlink-samples (macos-12)	7m 4s
neko-samples (3.4.7, macos-12)	4m 15s
neko-samples (4.2.5, windows-latest)	6m 49s
neko-samples (4.2.5, ubuntu-20.04)	3m 10s
neko-samples (4.2.5, macos-12)	4m 23s
notify	3s
	2h 15m 23s

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