build(deps): bump github.com/jackc/pgtype from 1.7.0 to 1.8.1

Bumps [github.com/jackc/pgtype](https://github.com/jackc/pgtype) from 1.7.0 to 1.8.1.
- [Release notes](https://github.com/jackc/pgtype/releases)
- [Changelog](https://github.com/jackc/pgtype/blob/master/CHANGELOG.md)
- [Commits](https://github.com/jackc/pgtype/compare/v1.7.0...v1.8.1)

---
updated-dependencies:
- dependency-name: github.com/jackc/pgtype
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

vendor/github.com/jackc/pgx/v4/tx.go

@@ -42,7 +42,12 @@ type TxOptions struct {
 	DeferrableMode TxDeferrableMode
 }
 
+var emptyTxOptions TxOptions
+
 func (txOptions TxOptions) beginSQL() string {
+	if txOptions == emptyTxOptions {
+		return "begin"
+	}
 	buf := &bytes.Buffer{}
 	buf.WriteString("begin")
 	if txOptions.IsoLevel != "" {