Another one snuck in there, see #4175
Revert "update gemspec for metasploit-credential"
This reverts commit 14514d7b8b, reversing
changes made to 6653d5e913.
MSP-11578
This will allow Metasploit Pro to use the
metasploit-framework-db.gemspec to ensure it has the correct version of
gems that were previously only in metasploit-framework's Gemfile and so
weren't being checked for version compatibility when Pro used
metasploit-framework.gemspec.