NIFI-7610 Updated dockerhub readme to latest nifi version
NIFI-7610 Updated dockerhub readme to latest nifi version

Signed-off-by: Matthew Burgess <mattyb149@apache.org>

This closes #4394

pvillard31/nifi,pvillard31/nifi,pvillard31/nifi,MikeThomsen/nifi,mattyb149/nifi,pvillard31/nifi,jfrazee/nifi,MikeThomsen/nifi,pvillard31/nifi,MikeThomsen/nifi,mattyb149/nifi,pvillard31/nifi,mattyb149/nifi,MikeThomsen/nifi,jfrazee/nifi,mattyb149/nifi,jfrazee/nifi,MikeThomsen/nifi,jfrazee/nifi,MikeThomsen/nifi,jfrazee/nifi,jfrazee/nifi,mattyb149/nifi,jfrazee/nifi,pvillard31/nifi,jfrazee/nifi,pvillard31/nifi,MikeThomsen/nifi,mattyb149/nifi,mattyb149/nifi