Removeschardet as a dependency, standardizing oncharset-normalizer.

This involved:

• Changingchardet tocharset-normalizer in our base dependency file
• Updating the code (in only one place) wherechardet was used
• pip-compiling to update our published dependency tree
• Updating one test...charset-normalizer misdiagnosed the encoding of a file used as a test fixture. My guess is that the ~10 characters in the file were not enough forcharset-normalizer to do a proper inference, so I re-encoded another slightly longer file that's also used for encoding testing, and it got that one.