fix(autoware.repos): use main branch of ros2_socketcan

[xmfcx]

Description

• fix(socket_can_receiver): support variable-length CAN FD frames ros2_socketcan#50

is merged, and the branch was auto-removed. We can now use the main branch of the repository.

In the future, we should do a quick release and use it from the tag.

But right now the autoware.repos points to a branch that doesn't exist.

We should quickly merge this.

Tests performed

Not applicable.

Effects on system behavior

Not applicable.

Interface changes

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