Bug 573960 - POM and product version change for 4.21 release

Change-Id: Ib893e88bda52d9338df0c85c64925f12873b1c81
Signed-off-by: Sravan Kumar Lakkimsetti <sravankumarl@in.ibm.com>
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.releng/+/181376
25 files changed