do not show trailing whitespace by default

[williamstein]

It would be better if the option "Show trailing whitespace: show spaces at ends of lines" in account preferences https://cocalc.com/settings were off by default for new accounts.

This is easy to change here: https://github.com/sagemathinc/cocalc/blob/master/src/packages/util/db-schema/accounts.ts#L220