julia> fig.plot.layout
layout with fields margin, template, xaxis1, xaxis2, yaxis1, and yaxis2
The [...] or hcat function for plots ignores showlegend (and possibly also other layout configurations).
julia> relayout!(fig, showlegend=false)
fixes this in your case. The [...] or hcat functions are Julia only methods for creating subplots. The Plotly-supported methods are more tedious, but are flexible and perhaps have less surprises.