Fix formatting issues with LMS account activation email.

This removes extra whitespace in the body of the LMS account activation email.

ENT-388

lms/templates/emails/activation_email.txt

 <%! from django.utils.translation import ugettext as _ %>
-${_("You're almost there!  Use the link to activate your account to access engaging, high-quality "
-"{platform_name} courses.  Note that you will not be able to log back into your account until "
+${_("You're almost there! Use the link to activate your account to access engaging, high-quality "
+"{platform_name} courses. Note that you will not be able to log back into your account until "
 "you have activated it.").format(platform_name=platform_name)}
 
 % if is_secure:
-  https://${ site }/activate/${ key }
+https://${ site }/activate/${ key }
 % else:
-  http://${ site }/activate/${ key }
+http://${ site }/activate/${ key }
 % endif
 
 ${_("Enjoy learning with {platform_name}.").format(platform_name=platform_name)}