chore: remove negative "files" entry which confused Yarn (#1453)

Author: mdjastrzebski

package.json

@@ -29,8 +29,7 @@
     "jest-preset/",
     "typings/index.flow.js",
     "pure.js",
-    "dont-cleanup-after-each.js",
-    "!**/test-utils"
+    "dont-cleanup-after-each.js"
   ],
   "devDependencies": {
     "@babel/cli": "^7.19.3",