MDL-65809 upgrade: remove format_xxx_upgrade_remove_numsections

These functions were used only by deleted upgrade steps
so it's safe to proceed with straight deletion, considering
them internal. Deletion has been documented in corresponding
upgrade.txt files:

    - format_topics_upgrade_remove_numsections()
    - format_topics_upgrade_hide_extra_sections()
    - format_topics_upgrade_add_empty_sections()
    - format_weeks_upgrade_remove_numsections()
    - format_weeks_upgrade_hide_extra_sections()
    - format_weeks_upgrade_add_empty_sections()

course/format/topics/db/upgrade.php

@@ -33,16 +33,6 @@
 function xmldb_format_topics_upgrade($oldversion) {
     global $CFG, $DB;
 
-    require_once($CFG->dirroot . '/course/format/topics/db/upgradelib.php');
-
-    if ($oldversion < 2017020200) {
-
-        // Remove 'numsections' option and hide or delete orphaned sections.
-        format_topics_upgrade_remove_numsections();
-
-        upgrade_plugin_savepoint(true, 2017020200, 'format', 'topics');
-    }
-
     // Automatically generated Moodle v3.3.0 release upgrade line.
     // Put any upgrade step following this.
 

course/format/upgrade.txt

@@ -2,6 +2,16 @@ This files describes API changes for course formats
 
 Overview of this plugin type at http://docs.moodle.org/dev/Course_formats
 
+=== 3.9 ===
+
+* The following functions, previously used (exclusively) by upgrade steps are not available anymore because of the upgrade cleanup performed for this version. See MDL-65809 for more info:
+    - format_topics_upgrade_remove_numsections()
+    - format_topics_upgrade_hide_extra_sections()
+    - format_topics_upgrade_add_empty_sections()
+    - format_weeks_upgrade_remove_numsections()
+    - format_weeks_upgrade_hide_extra_sections()
+    - format_weeks_upgrade_add_empty_sections()
+
 === 3.8 ===
 
 * The following functions have been finally deprecated and can not be used anymore:

course/format/weeks/db/upgrade.php

@@ -34,15 +34,6 @@ function xmldb_format_weeks_upgrade($oldversion) {
     global $CFG, $DB;
 
     require_once($CFG->dirroot . '/course/format/weeks/lib.php');
-    require_once($CFG->dirroot . '/course/format/weeks/db/upgradelib.php');
-
-    if ($oldversion < 2017020200) {
-
-        // Remove 'numsections' option and hide or delete orphaned sections.
-        format_weeks_upgrade_remove_numsections();
-
-        upgrade_plugin_savepoint(true, 2017020200, 'format', 'weeks');
-    }
 
     if ($oldversion < 2017050300) {
         // Go through the existing courses using the weeks format with no value set for the 'automaticenddate'.