Update dependency @types/split2 to v4 (#2438)

Co-authored-by: elastic-renovate-prod[bot] <174716857+elastic-renovate-prod[bot]@users.noreply.github.com>

Author: elastic-renovate-prod[bot]

package.json

@@ -59,7 +59,7 @@
     "@types/ms": "0.7.34",
     "@types/node": "22.9.0",
     "@types/sinonjs__fake-timers": "8.1.5",
-    "@types/split2": "3.2.1",
+    "@types/split2": "4.2.3",
     "@types/stoppable": "1.1.3",
     "@types/tap": "15.0.12",
     "chai": "4.5.0",