Update heapless requirement from 0.8.0 to 0.9.0

[dependabot]

Updates the requirements on heapless to permit the latest version.

Release notes

Sourced from heapless's releases.

0.9.0

See the full changelog here: https://github.com/rust-embedded/heapless/blob/v0.9.0/CHANGELOG.md#v090---2025-04-28

Changelog

Sourced from heapless's changelog.

[v0.9.0] - 2025-04-28

Added

• Added bytes::Buf and bytes::BufMut implementations for Vec.
• Added format macro.
• Added String::from_utf16.
• Added is_full, recent_index, oldest, and oldest_index to HistoryBuffer
• Added is_full to BinaryHeap
• Added is_full to IndexMap
• Added is_full to IndexSet
• Added is_full to LinearMap
• Added infallible conversions from arrays to Vec.
• Added Vec::spare_capacity_mut.
• Added Extend impls for Deque.
• Added Deque::make_contiguous.
• Added VecView, the !Sized version of Vec.
• Added pool implementations for 64-bit architectures.
• Added IntoIterator implementation for LinearMap
• Added Deque::{get, get_mut, get_unchecked, get_unchecked_mut}.
• Added serde::Serialize and serde::Deserialize implementations to HistoryBuffer.
• Added Vec::drain.
• Added String::drain.
• Implemented DoubleEndedIterator for OldestOrdered.
• Added std Entry methods to indexmap Entry.
• Added StringView, the !Sized version of String.
• Added BinaryHeapView, the !Sized version of BinaryHeap.
• Added MpMcQueueView, the !Sized version of MpMcQueue.
• Added LinearMapView, the !Sized version of LinearMap.
• Added HistoryBufferView, the !Sized version of HistoryBuffer.
• Added DequeView, the !Sized version of Deque.
• Added QueueView, the !Sized version of Queue.
• Added SortedLinkedListView, the !Sized version of SortedLinkedList.
• Added implementation of Borrow and BorrowMut for String and Vec.
• Added Deque::{swap, swap_unchecked, swap_remove_front, swap_remove_back}.
• Make String::from_utf8_unchecked const.
• Implemented PartialEq and Eq for Deque.
• Added alloc feature to enable alloc-Vec interoperability.
• Added TryFrom<alloc::vec::Vec> impl for Vec.
• Added TryFrom<Vec> impl for alloc::vec::Vec.
• Added truncate to IndexMap.
• Added get_index and get_index_mut to IndexMap.
• Added String::uDisplay.
• Added CString.
• Added LenT generic to Vec<T, N> and VecView<T> to save memory when using a sane capacity value.
• Added the index_set module.
• Added the index_map module.
• Migrated Idx generic for SortedLinkedList to use the new LenType trait, allowing for Idx inference.
• Added similar LenT generic to String.
• Optimize size of zero capacity Vec<T, 0> to be 0 bytes

... (truncated)

Commits

• 021a544 Merge pull request #556 from zeenix/release-0.9.0
• 92b476a Release 0.9.0
• 481de15 CHANGELOG: fix formatting
• c544954 Merge pull request #564 from reitermarkus/queue-docs
• 133bdaa Clean up queue docs.
• f692384 Merge pull request #443 from reitermarkus/const-split
• 717c7b1 Merge pull request #548 from rust-embedded/arc-atomics
• c46858a Add changelog entry.
• f02e9a1 Arc needs atomics.
• 0c1e1c0 Don't deny warnings.
• Additional commits viewable in compare view

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[dependabot]

Superseded by #3.