Fix generate.sh to generate .html file from .txt file correctly

I renamed the generated files to remove 'httpbis-' to match the .xml file. (I can also
rename the .xml file.)

It looks like generate.sh was generating the .html file from a txt file on a web page.
Surely it should generate the .html file from the local .txt file? Fixed that.

Then I regenerated the .html file. It seems it was way out of sync from the .txt file.