docs: restore section template comments in `ndarray/base/diagonal` and `ndarray/last` #26841

Job	Run time
Manage labels	0s
Rebase this PR on top of develop branch	0s
Auto-fix lint errors	0s
Update copyright header years	0s
Check for required files	0s
Remove in-progress label	0s
Merge changes from develop branch into this PR	0s
	0s

Provide feedback