[Fix] fixed GPG key error in Dockerfile

[atinfinity]

Motivation

I resolved #7951.

Modification

I fixed GPG key. I applied open-mmlab/mmsegmentation#1534.
And, I checked by the following command.

cd mmdetection
docker build -t mmdetection -f docker/Dockerfile .

My environment is as follows.

• Ubuntu 22.04
• nvidia-driver-515
• Docker 20.10.16

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects, like MMDet or MMCls.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[CLAassistant]

All committers have signed the CLA.