Bump undici in /backstage in the npm_and_yarn group across 1 directory (

#56)

Bumps the npm_and_yarn group with 1 update in the /backstage directory: [undici](https://github.com/nodejs/undici).


Updates `undici` from 5.28.3 to 5.28.4
- [Release notes](https://github.com/nodejs/undici/releases)
- [Commits](nodejs/undici@v5.28.3...v5.28.4)

---
updated-dependencies:
- dependency-name: undici
  dependency-type: indirect
  dependency-group: npm_and_yarn
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

backstage/yarn.lock

@@ -22903,9 +22903,9 @@ undici-types@~5.25.1:
   integrity sha512-Ga1jfYwRn7+cP9v8auvEXN1rX3sWqlayd4HP7OKk4mZWylEmu3KzXDUGrQUN6Ol7qo1gPvB2e5gX6udnyEPgdA==
 
 undici@^5.24.0:
-  version "5.28.3"
-  resolved "https://registry.yarnpkg.com/undici/-/undici-5.28.3.tgz#a731e0eff2c3fcfd41c1169a869062be222d1e5b"
-  integrity sha512-3ItfzbrhDlINjaP0duwnNsKpDQk3acHI3gVJ1z4fmwMK31k5G9OVIAMLSIaP6w4FaGkaAkN6zaQO9LUvZ1t7VA==
+  version "5.28.4"
+  resolved "https://registry.yarnpkg.com/undici/-/undici-5.28.4.tgz#6b280408edb6a1a604a9b20340f45b422e373068"
+  integrity sha512-72RFADWFqKmUb2hmmvNODKL3p9hcB6Gt2DOQMis1SEBaV6a4MH8soBvzg+95CYhCKPFedut2JY9bMfrDl9D23g==
   dependencies:
     "@fastify/busboy" "^2.0.0"