Bump pillow from 5.1.0 to 9.0.0 in /wechat

Bumps [pillow](https://github.com/python-pillow/Pillow) from 5.1.0 to 9.0.0.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/main/CHANGES.rst)
- [Commits](python-pillow/Pillow@5.1.0...9.0.0)

---
updated-dependencies:
- dependency-name: pillow
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

wechat/requirements.txt

@@ -5,7 +5,7 @@ idna==2.6
 numpy==1.14.5
 opencv-python==3.4.1.15
 optionaldict==0.1.1
-Pillow==5.1.0
+Pillow==9.0.0
 pycrypto==2.6.1
 python-dateutil==2.7.3
 python-mimeparse==1.6.0