Pin numpy<2 on nightly builds (#361)

Author: vblagoje

.github/workflows/nightly.yml

@@ -63,6 +63,7 @@ jobs:
         # remove pip install pyzmq when this is resolved https://github.com/zeromq/pyzmq/issues/1764
         run: |
           apt-get update && apt-get install -y build-essential gcc libsndfile1 ffmpeg && rm -rf /var/lib/apt/lists/*
+          pip install "numpy<2"
           pip install pyzmq==23.2.1
           pip install nbconvert ipython
           pip install "pyworld<=0.2.12" espnet espnet-model-zoo pydub