make tutorial headings consistent

Author: afeld

hw_0.ipynb

@@ -192,7 +192,7 @@
    "source": [
     "Now [turn in the assignment](https://python-public-policy.afeld.me/en/{{school_slug}}/assignments.html).\n",
     "\n",
-    "## Tutorials, Continued\n",
+    "## Tutorials, continued\n",
     "\n",
     "[Kaggle](https://www.kaggle.com/) is a data science platform that has various [tutorials](https://www.kaggle.com/learn/overview) and [competitions](https://www.kaggle.com/competitions), which you may want to go back to later. You are welcome to create a Kaggle account to save your progress, but it's not required.\n",
     "\n",

hw_2.ipynb

@@ -221,7 +221,7 @@
    "source": [
     "Now [turn in the assignment](https://python-public-policy.afeld.me/en/{{school_slug}}/assignments.html).\n",
     "\n",
-    "## Tutorials\n",
+    "## Tutorials, continued\n",
     "\n",
     "- [Pythonic Data Cleaning With Pandas and NumPy](https://realpython.com/python-data-cleaning-numpy-pandas/)\n",
     "- [\"You’re Not Mapping Rats, You're Mapping Gentrification\"](https://deadspin.com/you-re-not-mapping-rats-you-re-mapping-gentrification-1835005060/) — article about bias in 311 data\n",