Change "Add another user" to "Add a domain manager" (#1386)

* Change "Add another user" to "Add a domain manager"

* Change "Add another user" to "Add a domain manager"

* Update test_views.py to change "Add another user" to "Add a domain manager"

src/registrar/templates/domain_add_user.html

@@ -4,10 +4,10 @@
 {% block title %}Add another user{% endblock %}
 
 {% block domain_content %}
-  <h1>Add another user</h1>
+  <h1>Add a domain manager</h1>
 
   <p>You can add another user to help manage your domain. They will need to sign
-  into the .gov registrar with their Login.gov account.
+  in to the .gov registrar with their Login.gov account.
   </p>
 
   <form class="usa-form usa-form--large" method="post" novalidate>

src/registrar/templates/domain_users.html

@@ -53,7 +53,7 @@
   <a class="usa-button usa-button--unstyled" href="{% url 'domain-users-add' pk=domain.id %}">
     <svg class="usa-icon" aria-hidden="true" focusable="false" role="img" width="24" height="24">
       <use xlink:href="{%static 'img/sprite.svg'%}#add_circle"></use>
-    </svg><span class="margin-left-05">Add another user</span>
+    </svg><span class="margin-left-05">Add a domain manager</span>
   </a>
   </section>
 

src/registrar/tests/test_views.py

@@ -1305,12 +1305,12 @@ class TestDomainManagers(TestDomainOverview):
     def test_domain_managers_add_link(self):
         """Button to get to user add page works."""
         management_page = self.app.get(reverse("domain-users", kwargs={"pk": self.domain.id}))
-        add_page = management_page.click("Add another user")
-        self.assertContains(add_page, "Add another user")
+        add_page = management_page.click("Add a domain manager")
+        self.assertContains(add_page, "Add a domain manager")
 
     def test_domain_user_add(self):
         response = self.client.get(reverse("domain-users-add", kwargs={"pk": self.domain.id}))
-        self.assertContains(response, "Add another user")
+        self.assertContains(response, "Add a domain manager")
 
     def test_domain_user_add_form(self):
         """Adding an existing user works."""