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" } %>

spec/system/emails_spec.rb

@@ -329,7 +329,7 @@ describe "Emails" do
       login_as_manager
       visit new_management_user_invite_path
 
-      fill_in "emails", with: " john@example.com, ana@example.com,isable@example.com "
+      fill_in "Emails", with: " john@example.com, ana@example.com,isable@example.com "
       click_button "Send invitations"
 
       expect(page).to have_content "3 invitations have been sent."

spec/system/user_invites_spec.rb

@@ -5,7 +5,7 @@ describe "User invites" do
     login_as_manager
     visit new_management_user_invite_path
 
-    fill_in "emails", with: "john@example.com, ana@example.com, isable@example.com"
+    fill_in "Emails", with: "john@example.com, ana@example.com, isable@example.com"
     click_button "Send invitations"
 
     expect(page).to have_content "3 invitations have been sent."