docs: Use Docker 20.10 instead of 19.03 on docker build
Avoids GitLab users to use insecure Docker images.
- cf. &8060 (closed)
Signed-off-by: Takuya Noguchi takninnovationresearch@gmail.com
Edited by Takuya Noguchi
Avoids GitLab users to use insecure Docker images.
Signed-off-by: Takuya Noguchi takninnovationresearch@gmail.com