Fix case-sensitivity when comparing SPDX expressions

[sschuberth]

Section 4 over here states that SPDX licenses should be matches case-insensitively. However, this test currently fails:

        val actualExpression = SpdxExpression.parse("CDDL-1.1 OR GPL-2.0-only WITH Classpath-Exception-2.0").normalize()
        val expectedExpression = SpdxExpression.parse("CDDL-1.1 OR GPL-2.0-only WITH Classpath-exception-2.0").normalize()

        actualExpression shouldBe expectedExpression

Note the "E" vs "e" in "Exception".

When fixing this, we should discuss whether the test should also succeed without calling .normalize() on the expressions beforehand. I'd argue yes, the test should succeed also then, as the default behavior of comparing expressions should not consider the capitalization.