SPDX 2.3: LicenseRefs should not be case insensitive

According to the spec license expressions case sensitivity section, SPDX license IDs should be treated as case insensitive while LicenseRef's should be considered case sensitive.

Currently, if 2 license refs are found that differ only in case, an error is generated.

This situation should be allowed.

For example:

{
      "licenseId": "LicenseRef-BSD-3-clause-GENERIC",
      "extractedText": "NOASSERTION",
      "name": "BSD-3-clause-GENERIC"
    },
[...]
    {
      "licenseId": "LicenseRef-BSD-3-clause-generic",
      "extractedText": "NOASSERTION",
      "name": "BSD-3-clause-generic"
    },

should be allowed.

The error generated is Analysis exception processing SPDX file: Object URI ...#LicenseRef-BSD-3-clause-generic already exists.

No source file or test is named in the issue. Start by locating the code that reports duplicate Object URIs for LicenseRefs and the existing analysis tests; reproduce the case with two refs differing only by case, then confirm both are accepted while SPDX license IDs retain case-insensitive handling.