scripts/pkgdep.sh: fix default Golang version

There's no such version available as 1.21.

Signed-off-by: Karol Latecki <karol.latecki@intel.com>
Change-Id: I79b8513e33b88345601744ffaa24242e7474c131
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/19918


Reviewed-by: Krzysztof Karas <krzysztof.karas@intel.com>
Community-CI: Mellanox Build Bot
Reviewed-by: Marek Chomnicki <marek.chomnicki@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Pawel Piatek <pawelx.piatek@intel.com>
Reviewed-by: Kamil Godzwon <kamilx.godzwon@intel.com>
Reviewed-by: Konrad Sztyber <konrad.sztyber@intel.com>
Reviewed-by: Michal Berger <michal.berger@intel.com>
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>