Bump version to 1.4.3 for PyPI release

[SaintFresh]

Summary:

This pull request bumps the basicsr version to 1.4.3 to trigger a new release on PyPI. The new release will include an important fix for a torchvision import error that affects users relying on the latest PyPI version.

Issue:

The current version of basicsr (1.4.2) on PyPI is missing a fix for a ModuleNotFoundError related to importing the rgb_to_grayscale function from torchvision. This fix is already present in the main branch of the repository, but it hasn't been released to PyPI yet. (e.g. GFPGAN / ESRGAN in their colab notebook)

Solution:

By bumping the version number in the VERSION file, this pull request will trigger a new release on PyPI, making the fix available to all users who install basicsr through pip.

Testing:

I have confirmed that this fix works correctly in my local environment.

[DLesmes]

Who can review those checks to approve this PR @SaintFresh ?? It would be very usefull to have this new version available 🤔