Update version to Custom-v11.3 #1337

Job	Run time
build (base)	3m 12s
build-gcc-heli	2m 57s
build (clang)	4m 2s
autotest-heli (sitltest-heli)	6m 46s
autotest (sitltest-copter-tests1a)	11m 37s
autotest (sitltest-copter-tests1b)	11m 28s
autotest (sitltest-copter-tests1c)	14m 15s
autotest (sitltest-copter-tests1d)	13m 37s
autotest (sitltest-copter-tests1e)	13m 6s
autotest (sitltest-copter-tests2a)	10m 43s
autotest (sitltest-copter-tests2b)	35m 13s
	2h 6m 56s

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