tensorflow builds should use libjpeg-turbo

[pgunn]

Following the conda-forge migration to libjpeg-turbo:
conda-forge/opencv-feedstock#354

It'd be good to have the tensorflow builds from Continuum do the same so those of us mixing repos (I know this is not recommended, but it is necessary in some cases) have at least a reasonable shot at being able to use Continuum's tensorflow on Windows with packages from conda-forge (which now all pretty much use libjpeg-turbo).

Nowadays a fairly simple environment file, something like this:

channels:
- defaults
- conda-forge
dependencies:
- python >=3.10
- numpy
- opencv >=4.7.0
- tensorflow >=2.4.0

fails to resolve on Windows because conda-forge's opencv uses libjpeg-turbo, and recent tensorflow builds on Windows are only available on the Continuum channels, which still use libjpeg, which leads to a conflict.