Delete data/validate

Remove the validation dataset - we will use the dev dataset as our validation set during training

data/validate/2_3_mix_extract.tar

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:e6bce7b4431f5f15d6818a5f3458901a2a25386b094678896a549d6781501b4a
-size 949237760