fix(countries): normalise postal_code_format alternative-separator to | (BM, TW)

The convention used by GB/GG/IM/JE/BH/IR/LB/NL/PY/SH/AU-territories is to
separate alternative postal code formats with the pipe character. Two
outliers used non-standard separators:

  BM  '@@ ## or @@ @@'    -> '@@ ##|@@ @@'
  TW  '###/#####/######'  -> '###|#####|######'

Pure-cosmetic — neither postal_code_regex changes, no postcode rows touched,
no FK or geometry impact. This makes downstream postal-format parsers (e.g.
csc-validator) consistent across all 13 multi-format countries.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: dr5hn

contributions/countries/countries.json

@@ -1732,7 +1732,7 @@
     "subregion_id": 6,
     "nationality": "Bermudian, Bermudan",
     "area_sq_km": 53.0,
-    "postal_code_format": "@@ ## or @@ @@",
+    "postal_code_format": "@@ ##|@@ @@",
     "postal_code_regex": "^([A-Z]{2}\\s?[A-Z0-9]{2})$",
     "timezones": [
       {
@@ -14384,7 +14384,7 @@
     "subregion_id": 12,
     "nationality": "Chinese, Taiwanese",
     "area_sq_km": 35980.0,
-    "postal_code_format": "###/#####/######",
+    "postal_code_format": "###|#####|######",
     "postal_code_regex": "^(\\d{3}(?:\\d{2,3})?)$",
     "timezones": [
       {