Update go-sql-driver/mysql to v1.7.1 (#6976)

This update pulls in changes that we contributed upstream, which should
smooth interactions between Boulder and ProxySQL.

Release notes:
https://github.com/go-sql-driver/mysql/releases/tag/v1.7.1
Changelog:
go-sql-driver/mysql@v1.5.0...v1.7.1
Relevant change: go-sql-driver/mysql#1402

go.mod

@@ -12,7 +12,7 @@ require (
 	github.com/go-gorp/gorp/v3 v3.1.0
 	github.com/go-logr/stdr v1.2.2
 	github.com/go-redis/redis/v8 v8.11.5
-	github.com/go-sql-driver/mysql v1.5.0
+	github.com/go-sql-driver/mysql v1.7.1
 	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da
 	github.com/google/certificate-transparency-go v1.1.4
 	github.com/grpc-ecosystem/go-grpc-prometheus v1.2.0

go.sum

@@ -158,8 +158,8 @@ github.com/go-playground/universal-translator v0.18.1 h1:Bcnm0ZwsGyWbCzImXv+pAJn
 github.com/go-playground/universal-translator v0.18.1/go.mod h1:xekY+UJKNuX9WP91TpwSH2VMlDf28Uj24BCp08ZFTUY=
 github.com/go-redis/redis/v8 v8.11.5 h1:AcZZR7igkdvfVmQTPnu9WE37LRrO/YrBH5zWyjDC0oI=
 github.com/go-redis/redis/v8 v8.11.5/go.mod h1:gREzHqY1hg6oD9ngVRbLStwAWKhA0FEgq8Jd4h5lpwo=
-github.com/go-sql-driver/mysql v1.5.0 h1:ozyZYNQW3x3HtqT1jira07DN2PArx2v7/mN66gGcHOs=
-github.com/go-sql-driver/mysql v1.5.0/go.mod h1:DCzpHaOWr8IXmIStZouvnhqoel9Qv2LBy8hT2VhHyBg=
+github.com/go-sql-driver/mysql v1.7.1 h1:lUIinVbN1DY0xBg0eMOzmmtGoHwWBbvnWubQUrtU8EI=
+github.com/go-sql-driver/mysql v1.7.1/go.mod h1:OXbVy3sEdcQ2Doequ6Z5BW6fXNQTmx+9S1MCJN5yJMI=
 github.com/go-stack/stack v1.8.0/go.mod h1:v0f6uXyyMGvRgIKkXu+yp6POWl0qKG85gN/melR3HDY=
 github.com/gogo/protobuf v1.1.1/go.mod h1:r8qH/GZQm5c6nD/R0oafs1akxWv10x8SbQlK7atdtwQ=
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=