fix: use DROP MAPPING instead of deleting from pg_ts_config_map

The pre-upgrade hook failed with 'permission denied for table
pg_ts_config_map' because the migration runs as prosodyDBuser (a
non-superuser), and pg_ts_config_map is a PostgreSQL system catalog that
only superusers can DELETE from.

Replace the direct 'delete from pg_ts_config_map where ...' with the
equivalent non-superuser DDL 'ALTER TEXT SEARCH CONFIGURATION ... DROP
MAPPING IF EXISTS FOR <token types>', enumerating every token type the
block re-adds. Verified against postgres:15 as a non-superuser role: the
DELETE reproduces the exact error, DROP MAPPING IF EXISTS succeeds, and
the drop+re-add round-trip is idempotent across repeated runs.

Part-of: <http://gitlab.vnc.biz/uxf/vnctalk-prosody/-/merge_requests/3>

db-customization/prosody-13-new-deployment.sql

@@ -1280,9 +1280,15 @@ end $$;
 
 -- Reconcile mappings idempotently: remove all existing mappings for this
 -- configuration, then re-add the desired set (only if the dictionary exists).
+-- NOTE: do NOT delete from pg_ts_config_map directly — it is a PostgreSQL
+-- system catalog and only writable by superusers. ALTER ... DROP MAPPING
+-- IF EXISTS is the non-superuser DDL that achieves the same effect.
 do $$
 begin
-  delete from pg_ts_config_map where mapcfg = (select oid from pg_ts_config where cfgname = 'english_nostop');
+  alter text search configuration public.english_nostop drop mapping if exists
+    for asciiword, word, hword_part, hword_asciipart, asciihword, hword,
+         numword, email, url, host, sfloat, version, hword_numpart, numhword,
+         url_path, file, "float", "int", uint;
   if exists (select 1 from pg_ts_dict where dictname = 'english_stem_nostop') then
     alter text search configuration public.english_nostop add mapping for asciiword with public.english_stem_nostop;
     alter text search configuration public.english_nostop add mapping for word with public.english_stem_nostop;