chore(docker): Refine Dockerfile's ARG usage

[youtalk]

Description

I have standardized the ARG format in Dockerfile. This prevents issues where the command would incorrectly format as follows:

RUN source /opt/ros/"humble"/setup.bash

Additionally, I have removed duplicate instances of ARG ROS_DISTRO during this process.

Tests performed

Not applicable.

Effects on system behavior

Not applicable.

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