Schema Generators: change pluralization for licenseInfoInSnippet

[goneall]

Change from LicenseInfoInSnippets to LicenseInfosInSnippet.

This will probably require a special check in the pluralization code.

This may also require changes in the spdx-java-jackson-store code.

Initially reported as issue 804 in the SPDX spec repo.

[goneall]

This should be fixed in SPDX Spec version 3.0.

[goneall]

Since this would create an incompatibility in the schema - I'm not going to fix this until SPDX 3.0 where the spec states that all properties will be in the singular.