Fixes and updates in next/

Typo/format fixes were made in next/pw-change.html, next/register.html,
next/submit.html.

The screenshot for register step 6 (welcome email) was updated to
reflect a typo I had reported (after it was fixed). The html file still
has to be checked for rendering and that will be done soon.

next/submit.md

@@ -68,7 +68,7 @@ Now if you're done, log out.
 After the submission deadline is reached, you can log in to check the status of
 your submissions. Here is what it will look like when the judges have verified
 that your tarball / submission has been validated (NOT judged), by `txzchk(1)`
-and `chkentry(1)`.:
+and `chkentry(1)`:
 
 <img src="../png/submit-server-status-updated.png"
  alt="submit server status updated"