Fix step 1 on setting up local development environment

Created by: joshuabezaleel

Hi Sourcegraph team! Hope this message finds you all well 😄

I was setting up my machine for Sourcegraph local development environment and found few things that need to be tweaked first before it can run the local Sourcegraph instance as expected. These changes was based on my own experience and might not cater to the general step-by-step thus feel free to decline if you folks think that this might not be advantageous to others 😁

1. Turns out my machine hasn't installed ca-certificates yet (which was needed) and might be useful to add it to the list of the apt packages installed.
2. I think that the binary should be named migrate since the bash script for migration also used the migrate command instead of golang-migrate. Tried to rename the binary to golang-migrate and the migration didn't work (as expected).
3. Tiny typo on permissions.

Thank you lots in advance! 🙂