Reindent codes

[muzimuzhi]

All lines in sub-table of groups in manifest_setup() in l3build-manifest-setup.lua use three-space indentations (for example lines 60-61 in snippet below) and they are intact since I think that would change too many stable code lines.

l3build/l3build-manifest-setup.lua

Lines 57 to 61 in a4fc2f9

	function manifest_setup()
	local groups = {
	{
	subheading = "Repository manifest",
	description = [[