Fix the help text for cert_name_short and cert_name_long

This resolves the textual issue in [ECOM-2907] (https://openedx.atlassian.net/browse/ECOM-2907).
There will also be a data fix.

common/lib/xmodule/xmodule/course_module.py

@@ -496,9 +496,9 @@ class CourseFields(object):
     ## Course level Certificate Name overrides.
     cert_name_short = String(
         help=_(
-            "Use this setting only when generating PDF certificates. "
-            "Between quotation marks, enter the short name of the course to use on the certificate that "
-            "students receive when they complete the course."
+            'Use this setting only when generating PDF certificates. '
+            'Between quotation marks, enter the short name of the type of certificate that '
+            'students receive when they complete the course. For instance, "Certificate".'
         ),
         display_name=_("Certificate Name (Short)"),
         scope=Scope.settings,
@@ -506,9 +506,9 @@ class CourseFields(object):
     )
     cert_name_long = String(
         help=_(
-            "Use this setting only when generating PDF certificates. "
-            "Between quotation marks, enter the long name of the course to use on the certificate that students "
-            "receive when they complete the course."
+            'Use this setting only when generating PDF certificates. '
+            'Between quotation marks, enter the long name of the type of certificate that students '
+            'receive when they complete the course. For instance, "Certificate of Achievement".'
         ),
         display_name=_("Certificate Name (Long)"),
         scope=Scope.settings,