Revert "MDL-40829: courses heading: remove 'headerblock' class from header and fix heading levels"

This reverts commit 278d64572d272c776c564dcd743959c21ee20c8b.

Conflicts:
	theme/bootstrapbase/style/moodle.css
NOBUG/MDL-40829 - fix whitespace errors
MDL-37028 Fixed bug, orphaned modules are moved to the 0-section
MDL-41438 core renderer: additional patch to remove .main definition from all core themes
MDL-41438 - unbuilt less changes
MDL-41288 Wiki: add additional fix for heading level
MDL-41288 wiki: fix missing .rtl class for deleting comment button and improve page display for deleting comment
weekly release 2.6dev
MDL-41039 mod_quiz: Replace events_trigger to new events