Bump rsa from 3.1.4 to 4.7 in /python-server/guestbook

Bumps [rsa](https://github.com/sybrenstuvel/python-rsa) from 3.1.4 to 4.7.
- [Changelog](https://github.com/sybrenstuvel/python-rsa/blob/main/CHANGELOG.md)
- [Commits](sybrenstuvel/python-rsa@version-3.1.4...version-4.7)

---
updated-dependencies:
- dependency-name: rsa
  dependency-version: '4.7'
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

python-server/guestbook/requirements.txt

@@ -12,5 +12,5 @@ oauth2client>=1.3
 uritemplate>=0.6
 pyasn1==0.1.7
 pyasn1-modules==0.0.5
-rsa==3.1.4
+rsa==4.7
 simplejson>=2.5.0