Fix typos

Auditors: jace

Test plan: none
# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#	modified:   webapps/dashboards/templates/user-growth.html
#