[DEV] Normalize unnecessary executable bits on Python helper scripts

[Firstp1ck]

Summary

Some tracked files in this repo currently have executable mode (100755) even though they are not executed directly in our workflow.

We run Bash/Fish scripts via ./..., so executable bits on *.sh / *.fish are intentional.
Python scripts are run via uv or python ..., so +x is unnecessary for those files.

Affected files

dev/scripts/check_translation_keys.py
dev/scripts/update_version_announcement.py

Why this matters

• Reduces noisy permission-only diffs and review comments.
• Keeps file modes aligned with actual execution patterns.
• Improves repo consistency.

Proposed fix

Change both files from executable (100755) to regular (100644) and commit the mode change only.

Acceptance criteria

• Both Python files are 100644 in git.
• No content changes, only permission/mode changes.
• Bash/Fish scripts remain executable where needed.