[docs] Correct the basic syntax structure of the DISubrange example.

Notably, just close two of the debug info metadata nodes early rather
than leaving them open with `...` which won't ever lex correctly. And
add the missing `:` on the count labels.

Slowly progressing through all of the warnings on the documentation
build bot. Sorry to do this one commit at a time, but despite my best
efforts I can't trigger these errors locally.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@338982 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed