Update README.md (#33778)

Github -> GitHub

Author: eltociear

README.md

@@ -53,7 +53,7 @@ Management libraries can be identified by namespaces that start with `azure-mgmt
 ## Need help?
 
 * For detailed documentation visit our [Azure SDK for Python documentation](https://aka.ms/python-docs)
-* File an issue via [Github Issues](https://github.com/Azure/azure-sdk-for-python/issues)
+* File an issue via [GitHub Issues](https://github.com/Azure/azure-sdk-for-python/issues)
 * Check [previous questions](https://stackoverflow.com/questions/tagged/azure+python) or ask new ones on StackOverflow using `azure` and `python` tags.
 
 ### Community