Mark hashlib usages as not intended for security

[codecov[bot]]

Codecov Report

Merging #6264 (47e9bdb) into master (4cd94aa) will increase coverage by 0.00%. The diff coverage is 95.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #6264 +/- ## ======================================= Coverage 88.90% 88.90% ======================================= Files 161 161 Lines 11786 11793 +7 Branches 1913 1914 +1 ======================================= + Hits 10478 10485 +7 Misses 964 964 Partials 344 344 ``` | [Files](https://app.codecov.io/gh/scrapy/scrapy/pull/6264?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapy) | Coverage Δ | | |---|---|---| | [scrapy/pipelines/images.py](https://app.codecov.io/gh/scrapy/scrapy/pull/6264?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapy#diff-c2NyYXB5L3BpcGVsaW5lcy9pbWFnZXMucHk=) | `96.37% <100.00%> (-0.03%)` | :arrow_down: | | [scrapy/utils/misc.py](https://app.codecov.io/gh/scrapy/scrapy/pull/6264?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapy#diff-c2NyYXB5L3V0aWxzL21pc2MucHk=) | `98.70% <100.00%> (+<0.01%)` | :arrow_up: | | [scrapy/utils/request.py](https://app.codecov.io/gh/scrapy/scrapy/pull/6264?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapy#diff-c2NyYXB5L3V0aWxzL3JlcXVlc3QucHk=) | `90.00% <100.00%> (ø)` | | | [scrapy/pipelines/files.py](https://app.codecov.io/gh/scrapy/scrapy/pull/6264?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapy#diff-c2NyYXB5L3BpcGVsaW5lcy9maWxlcy5weQ==) | `79.73% <92.30%> (+0.47%)` | :arrow_up: |