Remove inaccurate comment about rule transition attrs.

Work towards composable starlark transitions: #22248.

PiperOrigin-RevId: 641254883
Change-Id: I75acc0ff8939f38fc4d97c1e1e56b0d0123e17c3

src/main/java/com/google/devtools/build/lib/analysis/starlark/StarlarkRuleTransitionProvider.java

@@ -108,7 +108,6 @@ private FunctionPatchTransition createTransition(
     ImmutableList<String> transitionOutputs = this.starlarkDefinedConfigTransition.getOutputs();
 
     for (Attribute attribute : rule.getAttributes()) {
-      // Store the value in an Optional, even if it's null.
       // If the value is present, even if it is null, add to the attribute map.
       Object val = attributeMapper.getRawAttributeValue(rule, attribute);
       if (val instanceof SelectorList<?> sl) {