[ci] Reset import-time baseline to CI-observed 91ms

CI measured 90.6ms after the lazy-import refactor lands. Set baseline to
91ms with 15% margin (ceiling 104.65ms, ~14ms headroom for GHA variance
over the observed measurement).

script/import_time_budget.json

@@ -1,5 +1,5 @@
 {
   "target_module": "esphome.__main__",
   "margin_pct": 15,
-  "cumulative_us": 82000
+  "cumulative_us": 91000
 }