Corrected another Sphinx capitlisation

Author: HChughtai

ch04packaging/04documentation.ipynb

@@ -92,7 +92,7 @@
    "source": [
     "We're going to document our \"greeter\" example from the previous section using docstrings with Sphinx.\n",
     "\n",
-    "There are various conventions for how to write docstrings, but the native sphinx one doesn't look nice when used with\n",
+    "There are various conventions for how to write docstrings, but the native Sphinx one doesn't look nice when used with\n",
     "the built in `help` system.\n",
     "\n",
     "In writing Greeter, we used the docstring conventions from NumPy.\n",