Avoid dependency on 'chai' through exported index

Fixes eclipse-glsp/glsp#1269

packages/protocol/src/utils/index.ts

@@ -17,5 +17,7 @@ export * from './array-util';
 export * from './di-util';
 export * from './disposable';
 export * from './event';
-export * from './test-util';
+// we do not export test-util to avoid a dependency on test frameworks such as chai
+// however, adopters can still access the file by accessing it through the complete path
+// export * from './test-util';
 export * from './type-util';