Bump tensorflow from 2.4.0 to 2.5.0 in /tensorflow/lite/micro/examples/magic_wand/train (#91)

Co-authored-by: Ndependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

tensorflow/lite/micro/examples/magic_wand/train/requirements.txt

 numpy==1.16.2
-tensorflow==2.4.0
+tensorflow==2.5.0