chore: add a test case for mdb_internal not followed by service name

Co-authored-by: Neal Beeken <neal.beeken@mongodb.com>

Author: gribnoysup

packages/mongodb-ns/src/index.spec.ts

@@ -99,6 +99,8 @@ describe('ns', function () {
   it('should identify internal namespaces', function () {
     assert.equal(ns('a').internal, false);
     assert.equal(ns('a.b').isInternal(), false);
+    assert.equal(ns('__mdb_internal.b').isInternal(), false);
+    assert.equal(ns('__mdb_internal').isInternal(), false);
     assert(ns('__mdb_internal_bla').internal);
     assert(ns('__mdb_internal_foo_bar').isInternal());
   });