Bump plugin-webperf-core from 2026.5.1 to 2026.6.0

Bumps [plugin-webperf-core](https://github.com/Webperf-se/plugin-webperf-core) from 2026.5.1 to 2026.6.0.
- [Release notes](https://github.com/Webperf-se/plugin-webperf-core/releases)
- [Commits](Webperf-se/plugin-webperf-core@2026.5.1...2026.6.0)

---
updated-dependencies:
- dependency-name: plugin-webperf-core
  dependency-version: 2026.5.3
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

package.json

@@ -24,7 +24,7 @@
     "plugin-javascript": "2026.5.1",
     "plugin-pagenotfound": "2026.5.1",
     "plugin-accessibility-statement": "2026.5.1",
-    "plugin-webperf-core": "2026.5.1"
+    "plugin-webperf-core": "2026.6.0"
   },
   "devDependencies": {
     "eslint": "10.4.0",