Clarify function comment for `erase` by stating that this idiom only works for…

Clarify function comment for `erase` by stating that this idiom only works for "some" standard containers.

If you use this idiom with `std::vector` or `absl::btree_map` you can end up either skipping elements or dereferencing an invalid iterator.

PiperOrigin-RevId: 639892758
Change-Id: Ic5c213667b4b1e8c39813ee237aaffe320a8eb27

absl/container/internal/raw_hash_set.h

@@ -3105,7 +3105,7 @@ class raw_hash_set {
   // this method returns void to reduce algorithmic complexity to O(1).  The
   // this method returns void to reduce algorithmic complexity to O(1).  The
   // iterator is invalidated, so any increment should be done before calling
   // iterator is invalidated, so any increment should be done before calling
   // erase.  In order to erase while iterating across a map, use the following
   // erase.  In order to erase while iterating across a map, use the following
-  // idiom (which also works for standard containers):
+  // idiom (which also works for some standard containers):
   //
   //
   // for (auto it = m.begin(), end = m.end(); it != end;) {
   // for (auto it = m.begin(), end = m.end(); it != end;) {
   //   // `erase()` will invalidate `it`, so advance `it` first.
   //   // `erase()` will invalidate `it`, so advance `it` first.