I have not been on the jewel, but on three NCL's + other cruise lines & nowhere is there a kettle provided.
I'm sure there were tea and coffee making facilities on our NCL Jewel cruise and I know for definite that we have the same facility on our cruise in March on the Norwegian Pearl. If you check the NCL website it may tell you.
Just come back from two weeks on the Jewel and we had a coffee maker that you could use for tea as well although it did still have a coffee after taste but there is copious amounts of coffee and tea in the garden cafe on deck 12 which you can take back to your room and its open almost all day and night. I would suggest taking your own tea bags though unless you like a weak tea. Have fun!!