Update developer-guide.adoc
Update developer-guide.adoc

Typo: "created created" (twice)

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

This closes #5168

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