CI apt-key add - deprecated

[GarethCabournDavies]

In #5262, copilot raised the following issue:

This workflow uses apt-key add -, which is deprecated on modern Ubuntu and may break as the runner images evolve. Prefer adding the repo key via gpg --dearmor into /etc/apt/keyrings/ and referencing it with signed-by= in the deb entry.

Copilot's suggested change

          wget -qO - https://research.cs.wisc.edu/htcondor/ubuntu/HTCondor-Release.gpg.key | sudo apt-key add -
          echo "deb http://research.cs.wisc.edu/htcondor/ubuntu/8.9/focal focal contrib" | sudo tee -a /etc/apt/sources.list
          echo "deb-src http://research.cs.wisc.edu/htcondor/ubuntu/8.9/focal focal contrib" | sudo tee -a /etc/apt/sources.list
          sudo apt-get -o Acquire::Retries=3 update
          sudo apt-get -o Acquire::Retries=3 install minihtcondor
          sudo systemctl start condor
          sudo systemctl enable condor
      - name: install pegasus
        run: |
          wget -qO - https://download.pegasus.isi.edu/pegasus/gpg.txt | sudo apt-key add -
          echo "deb https://download.pegasus.isi.edu/pegasus/ubuntu noble main" | sudo tee -a /etc/apt/sources.list

to

          sudo mkdir -p /etc/apt/keyrings
          wget -qO- https://research.cs.wisc.edu/htcondor/ubuntu/HTCondor-Release.gpg.key | gpg --dearmor | sudo tee /etc/apt/keyrings/htcondor-archive-keyring.gpg > /dev/null
          echo "deb [signed-by=/etc/apt/keyrings/htcondor-archive-keyring.gpg] http://research.cs.wisc.edu/htcondor/ubuntu/8.9/focal focal contrib" | sudo tee /etc/apt/sources.list.d/htcondor.list > /dev/null
          sudo apt-get -o Acquire::Retries=3 update
          sudo apt-get -o Acquire::Retries=3 install minihtcondor
          sudo systemctl start condor
          sudo systemctl enable condor
      - name: install pegasus
        run: |
          sudo mkdir -p /etc/apt/keyrings
          wget -qO- https://download.pegasus.isi.edu/pegasus/gpg.txt | gpg --dearmor | sudo tee /etc/apt/keyrings/pegasus-archive-keyring.gpg > /dev/null
          echo "deb [signed-by=/etc/apt/keyrings/pegasus-archive-keyring.gpg] https://download.pegasus.isi.edu/pegasus/ubuntu noble main" | sudo tee /etc/apt/sources.list.d/pegasus.list > /dev/null

I dont know enough about this to implement the change, but it seemed important