Fix spelling in comment (#80).

borgmatic/hooks/data_source/snapshot.py

@@ -5,11 +5,11 @@ IS_A_HOOK = False
 
 def get_contained_directories(parent_directory, candidate_contained_directories):
     '''
-    Given a parent directory and a set of candiate directories potentially inside it, get the subset
-    of contained directories for which the parent directory is actually the parent, a grandparent,
-    the very same directory, etc. The idea is if, say, /var/log and /var/lib are candidate contained
-    directories, but there's a parent directory (logical volume, dataset, subvolume, etc.) at /var,
-    then /var is what we want to snapshot.
+    Given a parent directory and a set of candidate directories potentially inside it, get the
+    subset of contained directories for which the parent directory is actually the parent, a
+    grandparent, the very same directory, etc. The idea is if, say, /var/log and /var/lib are
+    candidate contained directories, but there's a parent directory (logical volume, dataset,
+    subvolume, etc.) at /var, then /var is what we want to snapshot.
 
     Also mutate the given set of candidate contained directories to remove any actually contained
     directories from it. That way, this function can be called multiple times, successively