Update to ruby-magic v0.5.4

What does this MR do and why?

There are no code changes here, but the main difference is to fix a problem with the release package that failed to include:

1. The tarball for libfile.
2. A patch to disable building of documentation and tests for libfile.

This should make installs more reliable and avoid the need for downloading from a remote mirror.

Relates to https://github.com/kwilczynski/ruby-magic/issues/28

Diff: https://my.diffend.io/gems/ruby-magic/0.5.3/0.5.4

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.