#1121 (v3.4.8) introduces regression in TS support in transactions

As already discussed in #1121: > @porsager / @maxcbc this caused a pretty serious regression, i.e. all sql calls within sql.begins are now broken: ``` sql.begin(async (sql) => { await sql`my query`; // <== error here: // TS2349: This expression is not callable. // Type TransactionSql<{}> has no call signatures. }); ``` > See Dimous's comment here: > https://github.com/porsager/postgres/commit/36a53f6eb6524284ac5cb1046348f0216e133ebc#commitcomment-170665877 > @maxcbc do you mind either preparing a revert, or fixing forward?