Make trace done callback return value void

Author: Stephen Belanger

docs/test.ts

@@ -372,7 +372,7 @@ tracer.trace('test', { service: 'foo', resource: 'bar', type: 'baz' }, () => {})
 tracer.trace('test', { measured: true }, () => {})
 tracer.trace('test', (span: Span) => {})
 tracer.trace('test', (span: Span, fn: () => void) => {})
-tracer.trace('test', (span: Span, fn: (err: Error) => string) => {})
+tracer.trace('test', (span: Span, fn: (err: Error) => void) => {})
 
 promise = tracer.trace('test', () => Promise.resolve())
 

index.d.ts

@@ -84,8 +84,8 @@ export declare interface Tracer extends opentracing.Tracer {
    * option is deprecated and has been removed in version 4.0.
    */
   trace<T> (name: string, fn: (span: Span) => T): T;
-  trace<T> (name: string, fn: (span: Span, done: (error?: Error) => string) => T): T;
-  trace<T> (name: string, options: TraceOptions & SpanOptions, fn: (span?: Span, done?: (error?: Error) => string) => T): T;
+  trace<T> (name: string, fn: (span: Span, done: (error?: Error) => void) => T): T;
+  trace<T> (name: string, options: TraceOptions & SpanOptions, fn: (span?: Span, done?: (error?: Error) => void) => T): T;
 
   /**
    * Wrap a function to automatically create a span activated on its