public void deleteSymbolReference(Symbol symbol) {
        Symbol definition = definitionOfReference.remove(symbol);
        if (definition != null) {
            List<Symbol> references = symbolReferences.get(definition);
            if (references != null) {
                references.remove(symbol);
            }
        }
    }
Deletes the symbol reference from the schema index.

@param symbol The symbol reference to be deleted.
integration/schema-language-server/language-server/src/main/java/ai/vespa/schemals/index/SchemaIndex.java