Fix template variable typo
Fix template variable typo

Should be email instead of username (see redash/templates/login.html:47)
moritz9/redash,chriszs/redash,44px/redash,denisov-vlad/redash,EverlyWell/redash,denisov-vlad/redash,alexanderlz/redash,moritz9/redash,moritz9/redash,rockwotj/redash,44px/redash,alexanderlz/redash,crowdworks/redash,getredash/redash,chriszs/redash,crowdworks/redash,getredash/redash,hudl/redash,chriszs/redash,getredash/redash,denisov-vlad/redash,crowdworks/redash,moritz9/redash,rockwotj/redash,alexanderlz/redash,crowdworks/redash,rockwotj/redash,denisov-vlad/redash,getredash/redash,44px/redash,EverlyWell/redash,alexanderlz/redash,denisov-vlad/redash,hudl/redash,rockwotj/redash,hudl/redash,chriszs/redash,44px/redash,EverlyWell/redash,EverlyWell/redash,hudl/redash,getredash/redash