fix: resolve the splice start index against the pre-splice length in array-methods plugin - #1315

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5, coverallsapp/github-action@8cbef1dea373ebce56de0a14c68d6267baa10b44. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/