utils/spdx: correctly detect non-deprecated licenses with plus

[kthchew]

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  • NOTE: ran brew tests --online --only=utils/spdx, not brew tests

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When running brew audit --strict FORMULA, it will warn you that a license is deprecated if it ends in a "+", even if it is not deprecated. When I tested an example from the documentation that was given as an example of a valid license (license "EPL-1.0+"), it was also showing this warning.

I found this over in Homebrew/homebrew-core#71682, when I found that "MPL-1.1+" was incorrectly showing a deprecated SPDX license warning. Essentially, valid_license? in utils/spdx.rb removed the "+" suffix when checking for validity, but deprecated_license? did not, causing something like "MPL-1.1+" to be marked as valid but deprecated.

These changes prevent the false positive and add tests related to this behavior.

[Bo98]

Thanks @kthchew for the fix and the extra tests too!