fix: OTEL_TRACES_EXPORTER typo (#5686)

Co-authored-by: Tyler Yahn <[email protected]>

exporters/autoexport/spans.go

@@ -55,7 +55,7 @@ func NewSpanExporter(ctx context.Context, opts ...SpanOption) (trace.SpanExporte
 }
 
 // RegisterSpanExporter sets the SpanExporter factory to be used when the
-// OTEL_TRACES_EXPORTERS environment variable contains the exporter name. This
+// OTEL_TRACES_EXPORTER environment variable contains the exporter name. This
 // will panic if name has already been registered.
 func RegisterSpanExporter(name string, factory func(context.Context) (trace.SpanExporter, error)) {
 	must(tracesSignal.registry.store(name, factory))