Branding: fix numbering in activated_sp email tmpl

Fix numbering in the activated_sp email template.

The step numbering was:

 3. Claim your administrative access
 5. Double check all information...

skipping step 4.  (And the email preamble was referring to the
nonexistent step 4 while really meaning step 3).

Fixed now.
Merge pull request #167 from University-of-Auckland/develop-fix-activatesp-email

Branding: fix numbering in activated_sp email tmpl