[AutoDiff] NFC: minor cleanup after TF-1077. (#28913)

Fix inaccurate test comment.

Author: dan-zheng

lib/Sema/CodeSynthesis.cpp

@@ -290,7 +290,7 @@ ConstructorDecl *swift::getOrCreateEffectiveMemberwiseInitializer(
   for (auto *member : nominal->getMembers()) {
     auto var = dyn_cast<VarDecl>(member);
     if (!var ||
-        !var->isMemberwiseInitialized(/*preferDeclaredProperties=*/true))
+        !var->isMemberwiseInitialized(/*preferDeclaredProperties*/ true))
       continue;
     accessLevel = std::min(accessLevel, var->getFormalAccess());
   }

test/Sema/differentiable_access_level.swift

@@ -1,9 +1,11 @@
 // SWIFT_ENABLE_TENSORFLOW
 // RUN: %target-swift-frontend -print-ast %s | %FileCheck %s
 
-// Test `Differentiable` derived conformances.
-// Verify access levels of synthesized `TangentVector` types and their memberwise initializers.
-// `TangentVector` memberwise initializer access level should match `TangentVector` access level.
+// TF-1077: Verify access levels of `TangentVector` types and their memberwise
+// initializers, synthesized during `Differentiable` derived conformances.
+
+// `TangentVector` memberwise initializer access level should default to true,
+// for usability.
 
 public struct PublicStruct: Differentiable {}
 internal struct InternalStruct: Differentiable {}