[ros_google_cloud_language] Fix for python3; Avoid attribute error

[tkmtnt7000]

Upstream dependendy: https://github.com/ros/rosdistro/pull/38053

I fixed analyze_text.py for python3.

• Avoid attribute error AttributeError: 'bytes' object has no attribute 'encode'
• Convert map function to list comprehensions for python3
• Use unidecode to convet non-ascii character to ascii character

I would like to add a test code to confirm whether change is valid or not, but I think it's difficult to add test on Github action because this node needs google credential json.

[tkmtnt7000]

Upstream PR has already merged.