fix: update license content filtering default case to be 'none' for no content returned

---------
Signed-off-by: Christopher Phillips <32073428+spiffcs@users.noreply.github.com>

syft/format/common/spdxhelpers/to_format_model_test.go

@@ -958,7 +958,7 @@ func Test_otherLicenses(t *testing.T) {
 				{
 					LicenseIdentifier: "LicenseRef-3f17782eef51ae86f18fdd6832f5918e2b40f688b52c9adc07ba6ec1024ef408",
 					// Carries through the syft-json license value when we shasum large texts
-					LicenseName:   "LicenseRef-sha256:3f17782eef51ae86f18fdd6832f5918e2b40f688b52c9adc07ba6ec1024ef408",
+					LicenseName:   "sha256:3f17782eef51ae86f18fdd6832f5918e2b40f688b52c9adc07ba6ec1024ef408",
 					ExtractedText: strings.TrimSpace(bigText),
 				},
 			},

syft/format/internal/spdxutil/helpers/license.go

@@ -73,7 +73,7 @@ func ParseLicenses(raw []pkg.License) (concluded, declared []SPDXLicense, otherL
 	for _, l := range raw {
 		candidate := createSPDXLicense(l)
 
-		// isCustomLicense determines if the candidate falls under https://spdx.github.io/spdx-spec/v2.3/other-licensing-information-detected/#
+		// this determines if the candidate falls under https://spdx.github.io/spdx-spec/v2.3/other-licensing-information-detected/#
 		// of the SPDX spec, where:
 		// - we should not have a complex SPDX expression
 		// - if a single license, it should not be a known license (on the SPDX license list)