fix CI: executorch example model test env is using older transformers, that does not support numpy 2.0

Author: yifan_shen3

backends/apple/coreml/scripts/install_requirements.sh

@@ -47,6 +47,11 @@ cmake --build "$COREMLTOOLS_DIR_PATH/build" --parallel
 
 echo "${green}ExecuTorch: Installing coremltools."
 pip install "$COREMLTOOLS_DIR_PATH"
+# CoreMLTools have started supporting numpy 2.0,
+# but ExecuTorch example model test env is still using older transformers,
+# so for now we will need to downgrade numpy to 1.x
+# TODO: Remove this numpy downgrade once later transformers starts to be used
+pip install numpy==1.26.4
 STATUS=$?
 if [ $STATUS -ne 0 ]; then
     echo "${red}ExecuTorch: Failed to install coremltools."