Sampling from flow raises deprecation warning

[timothygebhard]

Running the following minimal example:

import normflows as nf
import torch

torch.manual_seed(42)

flow = nf.NormalizingFlow(
    nf.distributions.DiagGaussian(1, trainable=False),
    [
        nf.flows.AutoregressiveRationalQuadraticSpline(1, 1, 1),
        nf.flows.LULinearPermute(1)
    ]
)

with torch.no_grad():
    samples_flow, _ = flow.sample(4)

print(samples_flow)

raises a UserWarning about an upcoming deprecation:

/Users/timothy/Desktop/normalizing-flows/normflows/flows/mixing.py:437: UserWarning: torch.triangular_solve is deprecated in favor of torch.linalg.solve_triangular and will be removed in a future PyTorch release.
torch.linalg.solve_triangular has its arguments reversed and does not return a copy of one of the inputs.
X = torch.triangular_solve(B, A).solution
should be replaced with
X = torch.linalg.solve_triangular(A, B). (Triggered internally at  /Users/runner/work/pytorch/pytorch/pytorch/aten/src/ATen/native/BatchLinearAlgebra.cpp:2189.)
  outputs, _ = torch.triangular_solve(

I will submit a PR shortly that fixes the issue 🙂