[AutoDiff] Remove raw_ostream & argument from IndexSubset::dump. (swiftlang#31675)

Remove `llvm::raw_ostream &` argument so that `IndexSubset::dump` can be called
in lldb without issue.

Author: dan-zheng

include/swift/AST/IndexSubset.h

@@ -207,7 +207,7 @@ class IndexSubset : public llvm::FoldingSetNode {
   }
 
   void print(llvm::raw_ostream &s = llvm::outs()) const;
-  SWIFT_DEBUG_DUMPER(dump(llvm::raw_ostream &s = llvm::errs()));
+  SWIFT_DEBUG_DUMPER(dump());
 
   int findNext(int startIndex) const;
   int findFirst() const { return findNext(-1); }

lib/AST/IndexSubset.cpp

@@ -86,7 +86,8 @@ void IndexSubset::print(llvm::raw_ostream &s) const {
   s << '}';
 }
 
-void IndexSubset::dump(llvm::raw_ostream &s) const {
+void IndexSubset::dump() const {
+  auto &s = llvm::errs();
   s << "(index_subset capacity=" << capacity << " indices=(";
   interleave(getIndices(), [&s](unsigned i) { s << i; },
              [&s] { s << ", "; });