fix(types): Fix typo in setBitrate method. (#48)

Fixes a typo in the type definitions. This is probably a big deal for typescript users.

Author: armand1m

typings/index.d.ts

@@ -1,12 +1,11 @@
 declare module '@discordjs/opus' {
 export class OpusEncoder {
 public constructor(rate: number, channels: number);
-
 public encode(buf: Buffer): Buffer;
 public decode(buf: Buffer): Buffer;
 public applyEncoderCTL(ctl: number, value: number): void;
 public applyDecoderCTL(ctl: number, value: number): void;
-public setBirate(bitrate: number): void;
+public setBitrate(bitrate: number): void;
 public getBitrate(): number;
 }
 }