chore(thumbor): update ffmpeg to 7.1.5

[Copilot]

The thumbor image was pinned to an outdated ffmpeg version no longer matching the latest security patch available for Debian trixie.

• Version bump
  • Updated ffmpeg from 7:7.1.4-0+deb13u1 to 7:7.1.5-0+deb13u1 in both the build and run stages of dockerfiles/thumbor/Dockerfile.

- ffmpeg=7:7.1.4-0+deb13u1 \
+ ffmpeg=7:7.1.5-0+deb13u1 \

[Copilot]

Pull request overview

Updates the thumbor Docker image to use the latest Debian trixie security-patched ffmpeg package version, keeping dependency pinning current for reproducible and secure builds.

Changes:

• Bumped ffmpeg from 7:7.1.4-0+deb13u1 to 7:7.1.5-0+deb13u1 in the build stage.
• Bumped ffmpeg from 7:7.1.4-0+deb13u1 to 7:7.1.5-0+deb13u1 in the runtime stage.

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