Update dependency chalk to v6

Author: renovate[bot]

package.json

@@ -43,7 +43,7 @@
     "@tryghost/mg-substack": "1.8.0",
     "@tryghost/mg-wp-xml": "0.17.2",
     "@tryghost/string": "0.3.5",
-    "chalk": "5.6.2",
+    "chalk": "6.0.0",
     "cli-table3": "0.6.5",
     "commander": "15.0.0",
     "conf": "15.1.0",