Remove outdated instructions to enable self-paced courses

This is now selectable in studio for all courses and the referenced configuration no longer exists.

Resolves #1326

Author: sarina

source/site_ops/install_configure_run_guide/configuration/enable_certificates.rst

@@ -376,8 +376,7 @@ Enable Automatic Certificate Generation
 
 It is suggested that automatic certificate generation
 be enabled in order to provide the best experience for learners.
-Particularly in self-paced courses (see :ref:`Enable Self Paced
-Courses`), your learners might not want to wait until an instructor
+Particularly in self-paced courses, your learners might not want to wait until an instructor
 initiates certificate generation; instead, they would typically expect
 to be able to download their certificates as soon as they achieve a
 passing grade. This can be achieved by enabling *auto_certificate_generation*

source/site_ops/install_configure_run_guide/configuration/enable_pacing.rst

@@ -20,7 +20,6 @@ configuration options.
    deprecated_add_course_talk_widget
    edx_search
    enable_certificates
-   enable_pacing
    enable_public_course
    enable_ccx
    enable_custom_course_settings