fix: exclude "struct/__init__.py" from test_frake8.py

[xygyo77]

Description

Exclude struct/init.py from test_frake8.py.

Related links

https://tier4.atlassian.net/browse/RT2-1985

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[ymski]

A new check for built-in module name shadowing (A005) has been added in flake8-builtins v2.5.0.　 (CHANGELOG)

By applying this PR, it has been confirmed that the A005 related issue is no longer raised.
LGTM.

[miyakoshi-dev]

[compare] ========== Result ==========
[compare] 1/3 file existence matches
[compare] OK. file existence matches
[compare] 2/3 yaml files
[compare] OK. yaml matches
[compare] 3/3 PNG files
[compare] OK. PNG matches
[compare] ====== ALL OK ==============
LGTM