Update ACL pin to 20.02 release branch
Update ACL pin to 20.02 release branch

Signed-off-by: James Conroy <ce41d179dd5a8468f6c1c79fd3299ea93291d455@arm.com>
Change-Id: Ifc7fe6e6272155a250a649adc22beaa876996abb

ARM-software/armnn,ARM-software/armnn,ARM-software/armnn