Remove it. On a tree that size the likely outcomes are all bad or not worth the risk/cost of growth opportunity. Maybe it holds to maturity, but even then the fruit quality/size will probably be short of what it will be on a mature tree. Meanwhile, you'll have pushed that maturity date out, possibly a season or more. One fruit now will come at a cost to the tree and future fruit.
I had a Sweet Tart mango grafted with something like a 1.5" trunk and I let it hold two fruits to near-maturity. I also had ST grafted to a mature tree, so I didn't really care if it died. Die it did early the next season, and the fruit I got to try only one season before the mature tree graft produced fruit was nothing close in quality/flavor.