Bump aquasecurity/trivy-action from 0.16.1 to 0.21.0 #313

Job	Run time
Check whether tests need to be run based on diff	17s
Build Antrea image to be used for Kind e2e tests	20m 5s
Build Flow Aggregator image to be used for Kind e2e tests	3m 26s
E2e tests on a Kind cluster on Linux with all features enabled	57m 33s
E2e tests on a Kind cluster on Linux (noEncap)	37m 23s
E2e tests on a Kind cluster on Linux with non default values (proxyAll=true, LoadBalancerMode=DSR...	47m 11s
E2e tests on a Kind cluster on Linux	45m 42s
API compatible with client version N-1	5m 38s
E2e tests on a Kind cluster on Linux for Flow Visibility	29m 5s
API compatible with client version N-2	6m 27s
E2e tests on a Kind cluster on Linux (hybrid)	37m 27s
NetworkPolicy conformance tests on a Kind cluster on Linux	11m 30s
Upgrade from Antrea version N-1	5m 56s
Upgrade from Antrea version N-2	5m 37s
Validate metrics in Prometheus document match running deployment's	2m 15s
Delete uploaded images	0s
	5h 15m 32s

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