Typo within How to Become a Patch Guru? in contributor-guide

This bug tracker is for errors with the documentation, use the following as a template and remove or add fields as you see fit. Convert [ ] into [x] to check boxes:

- [x] This doc is inaccurate in this way: Typo on the word 'download' which is spelled as 'dowloand'
- [ ] This is a doc addition request.
- [x] I have a fix to the document that I can paste below including example: input and output.

input: To download the full chain you need to download the top patch and Git will automatically dowloand all the dependent patches in the chain.

output: To download the full chain you need to download the top patch and Git will automatically download all the dependent patches in the chain.

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Release: on 2018-10-27 04:41
SHA: 32d98f5df56e765b8babcb3f33eea90f0b3a5383
Source: https://git.openstack.org/cgit/openstack/contributor-guide/tree/doc/source/code-and-documentation/patch-best-practices.rst
URL: https://docs.openstack.org/contributors/code-and-documentation/patch-best-practices.html