Fix typo

Author: kakirastern

tutorials/notebooks/quantities/quantities.ipynb

@@ -10,6 +10,11 @@
     "Ana Bonaca, Erik Tollerud, Jonathan Foster, Kris Stern\n",
     "\n",
     "## Learning Goals\n",
+    "1. Use `Quantity` objects to estimate a hypothetical galaxy's mass\n",
+    "2. Use `Quantity` objects such as data cubes to facilitate a full derivation of the total mass of a molecular cloud\n",
+    "3. Write functions that take `Quantity` objects instead of raw numbers or arrays\n",
+    "\n",
+    "## Detailed Breakdown of Learning Goals\n",
     "* Learn how to instantiate `astropy.units.Quantity` objects\n",
     "* Take advantage of constants in the `astropy.constants` library\n",
     "* Print formatted unit strings\n",