Fix client.fetchApplication (#1644)
Fix client.fetchApplication (#1644)

previously it returned: `this.api.oauth2.applications was not a function`, missed fixing with the api router change
appellation/discord.js,Lewdcario/discord.js,devsnek/discord.js,devsnek/discord.js,Drahcirius/discord.js,appellation/discord.js,SpaceEEC/discord.js,Drahcirius/discord.js,CodeMan99/discord.js,appellation/discord.js,robflop/discord.js,robflop/discord.js,zajrik/discord.js,Lewdcario/discord.js,hydrabolt/discord.js,Lewdcario/discord.js,CodeMan99/discord.js,hydrabolt/discord.js,hydrabolt/discord.js,robflop/discord.js,Drahcirius/discord.js,zajrik/discord.js,SpaceEEC/discord.js,CodeMan99/discord.js,devsnek/discord.js,SpaceEEC/discord.js,zajrik/discord.js