Fix URL and location for SPDX schema

Fixes #1042

Signed-off-by: Gary O'Neall <[email protected]>

Author: goneall

docs/conformance.md

@@ -263,7 +263,7 @@ following constraints:
     see:
     [ECMA-404](https://ecma-international.org/publications-and-standards/standards/ecma-404/)
     - The JSON Schema for SPDX can be found in the
-      [SPDX specification Git repository schemas directory](https://github.com/spdx/spdx-spec/blob/master/schemas/spdx-schema.json)
+      [SPDX specification GitHub pages](https://spdx.github.io/spdx-spec/v3.0/model/schema.json)
   - **Resource Description Framework** (RDF, also referred to as RDF/XML)
     see:
     [RDF 1.1 XML Syntax](https://www.w3.org/TR/rdf-syntax-grammar/)