Replace use of tf.Dimension.value, which has been deprecated in TF2.
Replace use of tf.Dimension.value, which has been deprecated in TF2.

PiperOrigin-RevId: 314395568
Change-Id: I29212e28642a063f7989297ecb8dd4f74a09bdcc

magenta/note-seq,magenta/note-seq,magenta/note-seq