Bump fibers from 5.0.1 to 5.0.3

Bumps [fibers](https://github.com/laverdet/node-fibers) from 5.0.1 to 5.0.3.
- [Release notes](https://github.com/laverdet/node-fibers/releases)
- [Commits](https://github.com/laverdet/node-fibers/commits)

---
updated-dependencies:
- dependency-name: fibers
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

package.json

@@ -37,7 +37,7 @@
     "textpattern-branding": "0.3.3"
   },
   "optionalDependencies": {
-    "fibers": "5.0.1"
+    "fibers": "5.0.3"
   },
   "browserslist": [
     "> 0.5%",