Drop outdated Hackage vs CPAN package counts

The package counts have grown to 15353 and 43351 respectively as of this
writing, hence the ratio has dropped from 5.6 to 2.8. Given the growth
of Hackage, the comparison does not seem as important anymore (does it
matter if you have 3 or 8 alternative libraries for the same purpose?).
Dropping package counts to avoid the need for continuous updates.

Author: Vilius Panevėžys

doc/intro.rst

@@ -156,8 +156,8 @@ Ruby Gems or Perl distributions. Each system has a notion of
 distributable packages, and has tools to manage the process of
 distributing and installing packages.
 
-Hackage is an online archive of Cabal packages. It is roughly comparable
-to CPAN but with rather fewer packages (around 5,000 vs 28,000).
+Hackage is an online archive of Cabal packages, roughly comparable to
+CPAN.
 
 Cabal is often compared with autoconf and automake and there is some
 overlap in functionality. The most obvious similarity is that the