[analyzer] Don't print the config count in debug.ConfigDumper

I think anyone who added a checker config wondered why is there a need
to test this. Its just a chore when adding a new config, so I removed
it.

To give some historic insight though, we used to not list **all**
options, but only those explicitly added to AnalyzerOptions, such as the
ones specified on the command line. However, past this change (and
arguably even before that) this line makes little sense.

There is an argument to be made against the entirety of
analyzer-config.c test file, but since this commit fixes some builtbots
and is landing without review, I wouldn't like to be too invasive.