change test manager to npm

Author: Worth Lutz

lib/create-library.test.js

@@ -14,7 +14,7 @@ const fixtures = [
     description: 'this is an auto-generated test module. please ignore.',
     repo: 'nala/my-test-library',
     license: 'MIT',
-    manager: 'yarn',
+    manager: 'npm',
     template: 'default',
     git: true
   },
@@ -24,7 +24,7 @@ const fixtures = [
     description: 'this is an auto-generated test module. please ignore.',
     repo: 'nala/my-test-library',
     license: 'MIT',
-    manager: 'yarn',
+    manager: 'npm',
     template: 'typescript',
     git: true
   }