Update supported versions in security policy #847

Job	Run time
Lint code	20s
Lint Helm chart	4s
Lint scripts	4s
Verify templating chart with default values	3s
Unit test code	18s
Test integration with Prometheus	2m 0s
Verify that Helm README is up to date	20s
Verify that Makefile section of README is up to date	8s
Build Linux binary	32s
Build Linux ARM binary	0s
Build Mac binary	0s
Build Windows binary	0s
Build Linux Docker image	29s
Build Linux ARM Docker image	0s
Test integration with Helm chart	2m 21s
Create GitHub release	0s
upload-binaries	0s
	6m 39s

Provide feedback