plaidML: upgrading version

requirements-cuda.txt

@@ -3,7 +3,7 @@ h5py==2.9.0
 Keras==2.2.4
 opencv-python==4.0.0.21
 tensorflow-gpu==1.12.0
-plaidml-keras==0.5.0
+plaidml-keras==0.6.0rc1
 scikit-image
 dlib==19.16.0
 tqdm

requirements-opencl.txt

@@ -3,7 +3,7 @@ h5py==2.9.0
 Keras==2.2.4
 opencv-python==4.0.0.21
 tensorflow==1.12.0
-plaidml-keras==0.5.0
+plaidml-keras==0.6.0rc1
 scikit-image
 tqdm
 ffmpeg-python==0.1.17