docs: add missing word

docs/tutorials/machine_learning.ipynb

@@ -10,7 +10,7 @@
     "## Create a `TaggedTable`\n",
     "\n",
     "First, we need to create a `TaggedTable` from the training data. `TaggedTable`s are used to train supervised machine learning models, because they keep track of the target\n",
-    "column. A `TaggedTable` can be created from a `Table` calling the `tag_columns` method:"
+    "column. A `TaggedTable` can be created from a `Table` by calling the `tag_columns` method:"
    ],
    "metadata": {
     "collapsed": false