ci: Bump tuya-device-sharing-sdk to 0.2.8

Although we support installing on older HA versions that have older
versions pinned, requirements-dev already specifies the HA 2026.2.3
version of pytest-homeassistant-custom-component, so we are anyway
installing that version.

requirements-dev.txt

@@ -8,5 +8,5 @@ pytest-cov
 pytest-mock
 ruff
 tinytuya~=1.17.6
-tuya-device-sharing-sdk~=0.2.4
+tuya-device-sharing-sdk~=0.2.8
 yamllint