Much too narrow an area for even a groundcover. Whatever might be planted will want to grow both under the fence into the neighboring property as well as over the pavers. And any plant, very drought tolerant or not, will need regular watering until fully established.

Just fill the area with pea gravel or for a more decorative look, river rock.

Hens 'n chicks. Or have you seen those sedum tiles you can buy at Lowe's or Home Depot? You can cut them in strips to fit any space. They would need some water to get established but eventually would be self-sufficient. As gg said above, the plants may eventually grow out onto the step stones. If that's a problem then I'd go with pea gravel as well. But then it may just become a welcome mat for weeds.