Remove entry about storage_take.

It's not available on production chains, even though it does exist in the code. For more details, see:
- paritytech/substrate#12781
- use-ink/ink#1522
- use-ink/cargo-contract#846

contracts.md

@@ -20,7 +20,6 @@
 
 ## Storage
 
-- added `take(key) -> Option<V>` that allows for removing elements from the storage while returning the value. Replaces `get` + `remove` pattern.
 - Remove `SpreadAllocate`, `SpreadLayout` and `PackedLayout` implementations (and derivations).
 - Derive `StorageLayout` in`std` feature for types that you want to store in `Mapping`s (see `Bulletin` struct in the Bulletin Board migration). It’s used when generating contract’s metadata.