Bump ajv and eslint in /legacy

Bumps [ajv](https://github.com/ajv-validator/ajv) to 6.12.6 and updates ancestor dependency [eslint](https://github.com/eslint/eslint). These dependencies need to be updated together.


Updates `ajv` from 5.5.2 to 6.12.6
- [Release notes](https://github.com/ajv-validator/ajv/releases)
- [Commits](https://github.com/ajv-validator/ajv/compare/v5.5.2...v6.12.6)

Updates `eslint` from 4.19.1 to 9.0.0
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/main/CHANGELOG.md)
- [Commits](https://github.com/eslint/eslint/compare/v4.19.1...v9.0.0)

---
updated-dependencies:
- dependency-name: ajv
  dependency-type: indirect
- dependency-name: eslint
  dependency-type: direct:development
...

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

legacy/package.json

@@ -8,7 +8,7 @@
         "proj4": "^2.7.5"
     },
     "devDependencies": {
-        "eslint": "^4.4.1"
+        "eslint": "^9.0.0"
     },
     "scripts": {
         "postinstall": "/bin/bash -c 'mkdir -p web/lib/{ol,ol-layerswitcher,proj4,extjs} && cp node_modules/openlayers-dist/{ol.js,ol.css} web/lib/ol/ && cp node_modules/ol-layerswitcher/dist/{ol-layerswitcher.js,ol-layerswitcher.css} web/lib/ol-layerswitcher/ && cp node_modules/proj4/dist/proj4.js web/lib/proj4/ && cp node_modules/extjs-gpl/build/ext-all.js web/lib/extjs/ && mkdir -p web/lib/extjs/classic && cp -r node_modules/extjs-gpl/build/classic/locale web/lib/extjs/classic/locale && cp -r node_modules/extjs-gpl/build/classic/theme-triton web/lib/extjs/classic/theme-triton && mkdir -p web/lib/extjs/packages/charts && cp -r node_modules/extjs-gpl/build/packages/charts/classic web/lib/extjs/packages/charts/classic'",