xml: T1748: cleanup <help> and </help> nodes not closing on the same line

Commit rVYOSONEXa6f82bb48491 ("T1748: vbash: beautify tab completion output/line breaks")
added a method to split the help string and insert newlines and leading tabs
in a deterministic way.

This commit cleans up the legacy implementations where leading whitespaces got
counted and added by humans in a try/error method.