Fix missing "for" attribute in user invitations label

Since the attribute was missing, the label wasn't correctly associated
with its field.

app/views/management/user_invites/new.html.erb

@@ -1,7 +1,7 @@
 <h2><%= t("management.user_invites.new.title") %></h2>
 
 <%= form_tag management_user_invites_path do %>
-  <label><%= t("management.user_invites.new.label") %></label>
+  <%= label_tag :emails, t("management.user_invites.new.label") %>
   <p class="help-text" id="emails-help-text"><%= t("management.user_invites.new.info") %></p>
   <%= text_area_tag "emails", nil, rows: 5,
                                    aria: { describedby: "emails-help-text" } %>