fix(instr-koa): export KoaLayerType enum correctly (#2873)

Author: cincauhangus

plugins/node/opentelemetry-instrumentation-koa/src/index.ts

@@ -16,9 +16,9 @@
 
 export { KoaInstrumentation } from './instrumentation';
 export { AttributeNames } from './enums/AttributeNames';
+export { KoaLayerType } from './types';
 export type {
   KoaInstrumentationConfig,
-  KoaLayerType,
   KoaRequestCustomAttributeFunction,
   KoaRequestInfo,
 } from './types';