fix: fuzzing/local-dev-helpers/Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade: - https://snyk.io/vuln/SNYK-DEBIAN12-TIFF-13019601 - https://snyk.io/vuln/SNYK-DEBIAN12-TIFF-13019601 - https://snyk.io/vuln/SNYK-DEBIAN12-TIFF-13019601 - https://snyk.io/vuln/SNYK-DEBIAN12-ZLIB-6008963 - https://snyk.io/vuln/SNYK-DEBIAN12-ZLIB-6008963

Author: snyk-bot

fuzzing/local-dev-helpers/Dockerfile

@@ -1,7 +1,7 @@
 # syntax=docker/dockerfile:1
 
 # Use the same Python version as OSS-Fuzz to accidental incompatibilities in test code
-FROM python:3.14.0-bookworm
+FROM python:3.15-rc-slim-trixie
 
 LABEL project="GitPython Fuzzing Local Dev Helper"