build(deps): bump @graphql-tools/merge from 9.1.6 to 9.1.9

Bumps [@graphql-tools/merge](https://github.com/ardatan/graphql-tools/tree/HEAD/packages/merge) from 9.1.6 to 9.1.9.
- [Release notes](https://github.com/ardatan/graphql-tools/releases)
- [Changelog](https://github.com/ardatan/graphql-tools/blob/master/packages/merge/CHANGELOG.md)
- [Commits](https://github.com/ardatan/graphql-tools/commits/@graphql-tools/merge@9.1.9/packages/merge)

---
updated-dependencies:
- dependency-name: "@graphql-tools/merge"
  dependency-version: 9.1.9
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

package-lock.json

@@ -41,7 +41,7 @@
     "@defra/hapi-secure-context": "^0.3.0",
     "@elastic/ecs-winston-format": "^1.5.3",
     "@graphql-tools/load-files": "^7.0.1",
-    "@graphql-tools/merge": "^9.0.17",
+    "@graphql-tools/merge": "^9.1.9",
     "@graphql-tools/schema": "^10.0.16",
     "@graphql-tools/utils": "^10.7.2",
     "@hapi/hapi": "^21.3.12",