Update for pyyaml 6.0 (#435)

* yaml.safe_load instead of yaml.load

* Use yaml.safe_load in converters __init__.py

Author: thesps

hls4ml/converters/__init__.py

@@ -93,7 +93,7 @@ def construct_keras_model(loader, node):
 
     print('Loading configuration from', config_file)
     with open(config_file, 'r') as file:
-        parsed_config = yaml.load(file, Loader=yaml.SafeLoader)
+        parsed_config = yaml.safe_load(file)
     return parsed_config
 
 def convert_from_config(config):

test/pytest/test_cnn_mnist.py

@@ -37,7 +37,7 @@ def mnist_model():
 def hls_model(settings):
   io_type = settings[0]
   strategy = settings[1]
-  config = yaml.load(open('../../example-models/config-files/qkeras_mnist_cnn_config.yml').read())
+  config = yaml.safe_load(open('../../example-models/config-files/qkeras_mnist_cnn_config.yml').read())
   config['KerasJson'] = '../../example-models/keras/qkeras_mnist_cnn.json'
   config['KerasH5'] = '../../example-models/keras/qkeras_mnist_cnn_weights.h5'
   config['OutputDir'] = 'hls4mlprj_cnn_mnist_{}_{}'.format(io_type, strategy)