[doc] fix(ldoc.ltp): extra-header tag arrangement

[Aire-One]

This fix the tag arrangement issue @Elv13 spotted following the merge of #3288.

As a side note, there is a block line 225-227 (after applying this patch):

#   if module.tags.include then
        $(M(ldoc.include_file(module.tags.include)))
#   end

I don't know what it is used for, I can't find an instance of @include in our codebase, and it seems this if statement is always evaluated to false (I tried to force the print of module.tags.include, and it was always empty).

@blueyed, git blame says you added these lines (6792415), what are this supposed to be used for? Should we move this block to a extra-header__section block?

[codecov]

Codecov Report

Merging #3318 (ba97397) into master (022be39) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3318   +/-   ##
=======================================
  Coverage   88.66%   88.66%           
=======================================
  Files         702      702           
  Lines       46668    46668           
=======================================
+ Hits        41377    41378    +1     
+ Misses       5291     5290    -1     

Flag	Coverage Δ
gcov	75.24% <ø> (ø)
luacov	91.47% <ø> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
lib/awful/widget/layoutlist.lua	91.44% <0.00%> (+0.65%)	⬆️