Bump google.golang.org/grpc from 1.67.1 to 1.68.0 #13527

Job	Run time
Tests (mysql:5.6, mongo:4.2, postgres:14, percona/pmm-server:2.0.0)	3m 58s
Tests (mysql:5.7, mongo:4.4, postgres:15, percona/pmm-server:2.0.1)	4m 5s
Tests (mysql:8.0, mongo:4.4, postgres:16, percona/pmm-server:2.1.0)	3m 54s
Tests (mysql:8.0, mongo:4.4, postgres:17rc1, percona/pmm-server:2.2.0)	3m 43s
Tests (percona:5.6, percona/percona-server-mongodb:4.2, perconalab/percona-distribution-postgresq...	4m 2s
Tests (percona:5.7, percona/percona-server-mongodb:4.4, perconalab/percona-distribution-postgresq...	4m 16s
Tests (percona:8.0, percona/percona-server-mongodb:4.4, perconalab/percona-distribution-postgresq...	4m 11s
Tests (mariadb:10.2, mongo:4.4, postgres:12, perconalab/pmm-server:dev-latest)	3m 55s
Tests (mariadb:10.3, percona/percona-server-mongodb:4.4, postgres:13, perconalab/pmm-server:dev-l...	4m 19s
Tests (mariadb:10.4, postgres:14, perconalab/pmm-server:dev-latest)	3m 58s
	40m 21s

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