change "Known Issue" to "Known issue"

Author: American-Dipper

articles/hdinsight/spark/apache-spark-python-package-installation.md

@@ -115,7 +115,7 @@ HDInsight cluster depends on the built-in Python environment, both Python 2.7 an
 
     ![Check Python version in Jupyter Notebook](./media/apache-spark-python-package-installation/check-python-version-in-jupyter.png)
 
-## Known Issue
+## Known issue
 
 There is a known bug for Anaconda version 4.7.11 and 4.7.12. If you see your script actions hanging at `"Collecting package metadata (repodata.json): ...working..."` and failing with `"Python script has been killed due to timeout after waiting 3600 secs"`. You can download [this script](https://gregorysfixes.blob.core.windows.net/public/fix-conda.sh) and run it as script actions on all nodes to fix the issue.