Improve Gravity description
Improve Gravity description

Thanks Finland for helping with the description.
sirDonovan/Pokemon-Showdown,sirDonovan/Pokemon-Showdown,urkerab/Pokemon-Showdown,svivian/Pokemon-Showdown,xfix/Pokemon-Showdown,svivian/Pokemon-Showdown,svivian/Pokemon-Showdown,xfix/Pokemon-Showdown,svivian/Pokemon-Showdown,Zarel/Pokemon-Showdown,Zarel/Pokemon-Showdown,urkerab/Pokemon-Showdown,Zarel/Pokemon-Showdown,sirDonovan/Pokemon-Showdown,xfix/Pokemon-Showdown,xfix/Pokemon-Showdown,xfix/Pokemon-Showdown,urkerab/Pokemon-Showdown,svivian/Pokemon-Showdown