Switch from husky v8 to v9

frontend/package.json

@@ -14,8 +14,7 @@
     "lint": "stylelint '**/*.scss' && prettier --check './src' && next lint",
     "licensecheck": "license-checker --excludePrivatePackages --production --onlyAllow 'MPL; MIT; BSD-3-Clause; BSD-2-Clause; 0BSD; Apache-2.0; ISC; Zlib; CC0; Unlicense; WTFPL; Unicode-DFS-2016;'",
     "test": "jest",
-    "postinstall": "msw init public/ --save",
-    "prepare": "if [ \"$ON_HEROKU\" != \"True\" ]; then cd .. && husky install frontend/.husky; fi"
+    "postinstall": "msw init public/ --save"
   },
   "dependencies": {
     "@fluent/bundle": "^0.18.0",

package.json

@@ -30,7 +30,8 @@
     "test:stage": "E2E_TEST_ENV=stage playwright test --retries=2",
     "test:prod": "E2E_TEST_ENV=prod playwright test --retries=2",
     "heroku-prebuild": "printf '{\"commit\":\"%s\", \"commit_link\":\"https://github.com/mozilla/fx-private-relay/commit/%s\"}\n' \"$SOURCE_VERSION\" \"$SOURCE_VERSION\" > version.json",
-    "heroku-postbuild": "cd frontend; NODE_ENV=\"development\" npm ci; npm run build"
+    "heroku-postbuild": "cd frontend; NODE_ENV=\"development\" npm ci; npm run build",
+    "prepare": "husky"
   },
   "homepage": "https://github.com/mozilla/fx-private-relay#readme"
 }