Remove unused CI variables (#27)

Author: emersonknapp

.github/workflows/build.yml

@@ -26,9 +26,7 @@ jobs:
     container:
       image: ghcr.io/ros-tooling/setup-ros-docker/setup-ros-docker-ubuntu-${{ matrix.ubuntu }}:latest
     env:
-      ROS_DISTRO: ${{ matrix.ros }}
       PIP_BREAK_SYSTEM_PACKAGES: 1
-      USE_MCAP_PIP: 1
       AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
       AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
       AWS_DEFAULT_REGION: us-west-2