MM-18636: fix wrong merge conflict (#12386)

I resolved a merge conflict incorrectly when submitting MM-18636, and
want to remove the unused code I left behind.

config/database.go

@@ -7,7 +7,6 @@ import (
 	"bytes"
 	"database/sql"
 	"io/ioutil"
-	"regexp"
 	"strings"
 
 	"github.com/jmoiron/sqlx"
@@ -28,8 +27,6 @@ import (
 // It is imposed by MySQL's default max_allowed_packet value of 4Mb.
 const MaxWriteLength = 4 * 1024 * 1024
 
-var tcpStripper = regexp.MustCompile(`@tcp\((.*)\)`)
-
 // DatabaseStore is a config store backed by a database.
 type DatabaseStore struct {
 	commonStore