Works fine for me in a fresh environment on Julia 1.7.2 and I get
julia> mean(LogLoss(tol=1e-4)(yhat, y[test]))
1.8421480783955033
which means you most l likely have either
a) outdated package versions (probably less likely given predict has always been defined afaik; or
b) loaded another package which exports predict and conflicts with MLJ’s predict (e.g. GLM)
Can you run the code in a fresh REPL session and a temp environment to isolate the issue?