fix(ci): Sanitize PR title by using ENV variable

[jwndlng]

We need to sanitize the PR title by leveraging an environment variable as an intermediate step to prevent potential script injection attacks. This additional measure enhances the security of the workflow.

[github-actions]

canbench 🏋 (dir: examples/btreemap_vs_hashmap)

No significant performance changes detected ✅

examples/btreemap_vs_hashmap/canbench_results.yml is up to date ✅

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Benchmark: insert_users
  total:
    instructions: 2.57 B (no change)
    heap_increase: 871 pages (no change)
    stable_memory_increase: 0 pages (no change)

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Benchmark: remove_users
  total:
    instructions: 2.07 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

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Benchmark: pre_upgrade_bench
  total:
    instructions: 729.05 M (-0.01%) (change within noise threshold)
    heap_increase: 519 pages (no change)
    stable_memory_increase: 184 pages (no change)

  serialize_state (scope):
    instructions: 729.05 M (-0.01%) (change within noise threshold)
    heap_increase: 519 pages (no change)
    stable_memory_increase: 0 pages (no change)

  writing_to_stable_memory (scope):
    instructions: 506 (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 184 pages (no change)

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[github-actions]

canbench 🏋 (dir: examples/fibonacci)

No significant performance changes detected ✅

examples/fibonacci/canbench_results.yml is up to date ✅

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Benchmark: fibonacci_20
  total:
    instructions: 2224 (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

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Benchmark: fibonacci_45
  total:
    instructions: 3011 (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------