Bump multidict from 6.3.2 to 6.4.3

Bumps [multidict](https://github.com/aio-libs/multidict) from 6.3.2 to 6.4.3.
- [Release notes](https://github.com/aio-libs/multidict/releases)
- [Changelog](https://github.com/aio-libs/multidict/blob/master/CHANGES.rst)
- [Commits](aio-libs/multidict@v6.3.2...v6.4.3)

---
updated-dependencies:
- dependency-name: multidict
  dependency-version: 6.4.3
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]