Bug 573960 - POM and product version change for 4.21 release

Change-Id: I9d7063f961475963c2d5e07132366e3f3bd3bcce
Signed-off-by: Sravan Kumar Lakkimsetti <sravankumarl@in.ibm.com>
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.text/+/181370
11 files changed