cmd/generate-analytics-api: remove merged_output

[cho-m]

Just a quick fix for Homebrew/formulae.brew.sh#1104

Not sure how to reproduce original result.merged_output behavior. By default Utils.popen_read sends stderr to /dev/null.

Did try a StringIO but wasn't successful, e.g.

stderr = StringIO.new
result = Utils.popen_read(..., err: stderr)

I was able to get some stderr via IO.pipe but not sure if best way, e.g.

stderr = ""
IO.pipe do |rd, wr|
  result = Utils.popen_read(..., err: wr)
  wr.close
  stderr = rd.read
end

[Bo98]

We'll want stderr printing of some form so I've just tweaked it so it just prints directly always.

The code that's erroring will only happen if something else is erroring, which will likely have the information needed in stderr.

[MikeMcQuaid]

Thanks @cho-m and @Bo98!