Update dependency pytype to v2020.7.20

[renovate[bot]]

This PR contains the following updates:

Package	Update	Change
pytype (source)	minor	==2020.6.1 -> ==2020.7.20

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Release Notes

google/pytype

### [`v2020.7.20`](https://togithub.com/google/pytype/compare/2020.07.14...2020.07.20) [Compare Source](https://togithub.com/google/pytype/compare/2020.07.14...2020.07.20) ### [`v2020.7.14`](https://togithub.com/google/pytype/compare/2020.06.26...2020.07.14) [Compare Source](https://togithub.com/google/pytype/compare/2020.06.26...2020.07.14) ### [`v2020.6.26`](https://togithub.com/google/pytype/compare/2020.06.01...2020.06.26) [Compare Source](https://togithub.com/google/pytype/compare/2020.06.01...2020.06.26)

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