chore(deps): update dependency @textlint/legacy-textlint-core to v15 (#110)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

package-lock.json

@@ -39,7 +39,7 @@
     "textlint-rule-helper": "^2.3.1"
   },
   "devDependencies": {
-    "@textlint/legacy-textlint-core": "^14.8.4",
+    "@textlint/legacy-textlint-core": "^15.1.1",
     "lint-staged": "^15.5.2",
     "prettier": "^3.5.3",
     "textlint": "14.8.4",