Set label in project header to "Project lead:" instead of only "Lead:" (#4570)

When a project exist the project header is used for submission detail
view as well. This spells out that what you see in the header is the
project lead, not the submission lead.

Author: frjo

hypha/apply/projects/templates/application_projects/partials/project_lead.html

@@ -6,9 +6,9 @@
        hx-get="{% url 'apply:projects:lead_update' object.submission.id %}"
        hx-target="#htmx-modal"
     >
-        <u>{% trans "Lead" %}: {{ object.lead }}</u>
+        <u>{% trans "Project lead" %}: {{ object.lead }}</u>
         {% heroicon_micro "pencil-square" class="inline ms-1" aria_hidden=true %}
     </a>
 {% else %}
-    <span>{% trans "Lead" %}: {{ object.lead }}</span>
+    <span>{% trans "Project lead" %}: {{ object.lead }}</span>
 {% endif %}