Disable `test_download_charngram_vectors` on Linux CI

[Nayef211]

• The test_vocab_from_raw_text_file test is failing on CI for linux platforms due to the following error urllib.error.HTTPError: HTTP Error 404: Not Found (see sample CI job)
• Will revert once https://github.com/pytorch/text/issues/2160 is resolved

[pytorch-bot[bot]]

:link: Helpful Links

:test_tube: See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/text/2161

• :page_facing_up: Preview Python docs built from this PR

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:x: 1 Failures

As of commit a66afc71d522c211dec5b07f5fbb71ed950719f2:

NEW FAILURES - The following jobs have failed:

* [Bandit](https://hud.pytorch.org/pr/pytorch/text/2161#4799995334) ([gh](https://github.com/pytorch/text/actions/runs/4799995334))

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