fix: use find_package to fix rolling build error

[xmfcx]

Follow up from:

• https://github.com/autowarefoundation/ros2_socketcan/pull/42

Attempts to fix:

• https://github.com/autowarefoundation/ros2_socketcan/actions/runs/8421904097/job/23059902100?pr=42#step:5:371

I don't know why is this necessary but without find_package(can_msgs REQUIRED) it cannot build with rolling.

[xmfcx]

Wrong judgement from my side.

It turns out this was coming from rosdep not resolving the package.xml things because I was in Ubuntu jammy and instead was asking for noble.

Instead, opened this PR:

• https://github.com/autowarefoundation/ros2_socketcan/pull/44