ci/package_checks: Add exception for EULA as a package license

[silkeh]

Summary

Add an exception for EULA, as that is used by the following packages:

hsa-amd-aqlprofile
intel-microcode
nvidia-470-glx-driver
nvidia-beta-driver
nvidia-developer-driver
nvidia-glx-driver
opencv

This is not a valid SPDX license identifier, but there is no valid alternative.

Resolves #2423

Test Plan

Verify the warning is no longer there:

$ ./common/CI/package_checks.py packages/i/intel-microcode/package.yml
Checking files: packages/i/intel-microcode/package.yml
Found 2 result(s), 1 warnings and 0 error(s)
INF packages/i/intel-microcode/package.yml:1: This package is included in the ISO. Consider validating the functionality in a newly built ISO.
WRN packages/i/intel-microcode/package.yml:1: Package release is not incremented by 1

[ermo]

LGTM!