Fix use of yaml.load()

The use of this function has been deprecated for a long time[0]. With
PyYAML==6.0 the call is now failing, so replace it with the safe
version.

[0] https://msg.pyyaml.org/load

Signed-off-by: Jens Harbott <frickler@offenerstapel.de>
Change-Id: I7a170262b50a5c80a516095b872d52e1bea5479d
diff --git a/tools/update_clouds_yaml.py b/tools/update_clouds_yaml.py
index 7be995e..74dcdb2 100755
--- a/tools/update_clouds_yaml.py
+++ b/tools/update_clouds_yaml.py
@@ -65,7 +65,7 @@
     def _read_clouds(self):
         try:
             with open(self._clouds_path) as clouds_file:
-                self._clouds = yaml.load(clouds_file)
+                self._clouds = yaml.safe_load(clouds_file)
         except IOError:
             # The user doesn't have a clouds.yaml file.
             print("The user clouds.yaml file didn't exist.")