deps: bump minimum ICU version to 73

Refs: v8/v8@d9715ad
PR-URL: #49639
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

tools/icu/icu_versions.json

@@ -1,3 +1,3 @@
 {
-    "minimum_icu": 71
+    "minimum_icu": 73
 }