Remove `CharIterator::operator->`.

An `operator->` that doesn't return a record type doesn't really serve a useful
purpose, and it is not required by the iterator concepts. I haven't been able
to find any usage in non-test code, so I'm removing it.

Even though the `pointer` type alias is now not being used anywhere, I'm keeping
it because otherwise some standard libraries don't accept `CharIterator` when
passed to `std::string::apend()`, for example.

PiperOrigin-RevId: 659832167
Change-Id: I5de183a01009bfd71c8477f2023973075be8d860

absl/strings/cord.h

@@ -641,7 +641,6 @@ class Cord {
     bool operator==(const CharIterator& other) const;
     bool operator!=(const CharIterator& other) const;
     reference operator*() const;
-    pointer operator->() const;
 
     friend Cord;
 
@@ -1659,10 +1658,6 @@ inline Cord::CharIterator::reference Cord::CharIterator::operator*() const {
   return *chunk_iterator_->data();
 }
 
-inline Cord::CharIterator::pointer Cord::CharIterator::operator->() const {
-  return chunk_iterator_->data();
-}
-
 inline Cord Cord::AdvanceAndRead(absl::Nonnull<CharIterator*> it,
                                  size_t n_bytes) {
   assert(it != nullptr);

absl/strings/cord_test.cc

@@ -2530,8 +2530,6 @@ static void VerifyCharIterator(const absl::Cord& cord) {
     EXPECT_EQ(*pre_iter, *post_iter);
     EXPECT_EQ(&*pre_iter, &*post_iter);
 
-    EXPECT_EQ(&*pre_iter, pre_iter.operator->());
-
     const char* character_address = &*pre_iter;
     absl::Cord::CharIterator copy = pre_iter;
     ++copy;