Change "dd" optional parameter 1m to 1M

[daikiojm]

I ran the code of the latest master branch, and in my environment the following error occurred.

*** MAKE SURE YOU SELECT THE CORRECT DISK *** *** Refer to the Readme if uncertain ***

Use disk [ 1, 2 ] #2 Unmounting Disk Volume TEST on disk2s1 unmounted Writing image Ctrl+T to see progress.. dd: invalid number: ‘1m’

It seems to be resolved by capitalizing the option of dd.