Update allennlp/models/multitask.py

Co-authored-by: James Barry <james.barry26@mail.dcu.ie>

allennlp/models/multitask.py

@@ -29,7 +29,7 @@ class MultiTaskModel(Model):
     right arguments to the right modules, but we allow you to specify these arguments yourself in
     case our inference code gets it wrong.
 
-    It the caller's responsibility to make sure that the backbone and all heads are compatible with
+    It is the caller's responsibility to make sure that the backbone and all heads are compatible with
     each other, and with the input data that comes from a `MultiTaskDatasetReader`.  We give some
     arguments in this class and in `MultiTaskDatasetReader` to help with plumbing the arguments in
     complex cases (e.g., you can change argument names so that they match what the backbone and