[Minor] Remove permission for execution from spark-shell.cmd

.cmd files in bin is not set permission for execution except for spark-shell.cmd.
Let's unify that.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #3983 from sarutak/fix-mode-of-cmd and squashes the following commits:

9d6eedc [Kousuke Saruta] Removed permission for execution from spark-shell.cmd