docs: remove reference to validation.rst in index.rst

Signed-off-by: Saquib Saifee <saquibsaifee2@gmail.com>

Author: saquibsaifee

docs/index.rst

@@ -45,7 +45,6 @@ If you're looking for a CycloneDX tool to run to generate (SBOM) software bill-o
    install
    architecture
    examples
-   validation
    contributing
    support
    changelog