settings_user_list_row: Remove redundant classes.

This commit Removes `deactivate-user-button` and
`reactivate-user-button` classes.

These classes were originally introduced in commits
50582b72b6 and
c0b3fb1bbe for the sole
purpose of styling. The associated styles were later removed
in 1c89c3e647 but the classes
themselves were mistakenly left behind.

Removing them has no effect in the functionality of the
buttons and there is no evidence of any bugs or regression
caused by their removal.

web/templates/settings/settings_user_list_row.hbs

@@ -58,7 +58,7 @@
                 {{> ../components/icon_button
                   icon="user-x"
                   intent="danger"
-                  custom_classes="deactivate deactivate-user-button"
+                  custom_classes="deactivate"
                   disabled=cannot_deactivate
                   }}
             </span>
@@ -67,7 +67,7 @@
                 {{> ../components/icon_button
                   icon="user-plus"
                   intent="success"
-                  custom_classes="reactivate reactivate-user-button"
+                  custom_classes="reactivate"
                   }}
             </span>
             {{/if}}