Update motor requirement from <3.0.0,>=2.5.1 to >=2.5.1,<4.0.0

Updates the requirements on [motor](https://github.com/mongodb/motor) to permit the latest version.
- [Release notes](https://github.com/mongodb/motor/releases)
- [Changelog](https://github.com/mongodb/motor/blob/master/doc/changelog.rst)
- [Commits](mongodb/motor@2.5.1...3.6.0)

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

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

requirements.txt

@@ -1,2 +1,2 @@
 fastapi-users >= 9.1.0
-motor >=2.5.1,<3.0.0
+motor >=2.5.1,<4.0.0