Bump pymodbus from 3.7.4 to 3.8.1

Bumps [pymodbus](https://github.com/pymodbus-dev/pymodbus) from 3.7.4 to 3.8.1.
- [Release notes](https://github.com/pymodbus-dev/pymodbus/releases)
- [Changelog](https://github.com/pymodbus-dev/pymodbus/blob/dev/CHANGELOG.rst)
- [Commits](pymodbus-dev/pymodbus@v3.7.4...v3.8.1)

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

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

requirements.txt

@@ -2,4 +2,4 @@ colorlog==6.9.0
 homeassistant==2024.10.3
 pip>=21.3.1
 ruff==0.8.4
-pymodbus==3.7.4
+pymodbus==3.8.1