Improves documentation on num_slashing_spans when calling `withdraw…

…_unbounded` in Staking. (paritytech#14185)

* gpestana/11714-num_slashing_spans_docs

* Update frame/staking/src/pallet/mod.rs

Co-authored-by: Kian Paimani <[email protected]>

* All calls that take num_slashing_span as parameters refer to comments on it

---------

Co-authored-by: Kian Paimani <[email protected]>

frame/staking/src/pallet/mod.rs

@@ -1040,15 +1040,24 @@ pub mod pallet {
 
 		/// Remove any unlocked chunks from the `unlocking` queue from our management.
 		///
-		/// This essentially frees up that balance to be used by the stash account to do
-		/// whatever it wants.
+		/// This essentially frees up that balance to be used by the stash account to do whatever
+		/// it wants.
 		///
 		/// The dispatch origin for this call must be _Signed_ by the controller.
 		///
 		/// Emits `Withdrawn`.
 		///
 		/// See also [`Call::unbond`].
 		///
+		/// ## Parameters
+		///
+		/// - `num_slashing_spans` indicates the number of metadata slashing spans to clear when
+		/// this call results in a complete removal of all the data related to the stash account.
+		/// In this case, the `num_slashing_spans` must be larger or equal to the number of
+		/// slashing spans associated with the stash account in the [`SlashingSpans`] storage type,
+		/// otherwise the call will fail. The call weight is directly propotional to
+		/// `num_slashing_spans`.
+		///
 		/// ## Complexity
 		/// O(S) where S is the number of slashing spans to remove
 		/// NOTE: Weight annotation is the kill scenario, we refund otherwise.
@@ -1377,6 +1386,11 @@ pub mod pallet {
 		/// Force a current staker to become completely unstaked, immediately.
 		///
 		/// The dispatch origin must be Root.
+		///
+		/// ## Parameters
+		///
+		/// - `num_slashing_spans`: Refer to comments on [`Call::withdraw_unbonded`] for more
+		/// details.
 		#[pallet::call_index(15)]
 		#[pallet::weight(T::WeightInfo::force_unstake(*num_slashing_spans))]
 		pub fn force_unstake(
@@ -1517,6 +1531,11 @@ pub mod pallet {
 		/// It can be called by anyone, as long as `stash` meets the above requirements.
 		///
 		/// Refunds the transaction fees upon successful execution.
+		///
+		/// ## Parameters
+		///
+		/// - `num_slashing_spans`: Refer to comments on [`Call::withdraw_unbonded`] for more
+		/// details.
 		#[pallet::call_index(20)]
 		#[pallet::weight(T::WeightInfo::reap_stash(*num_slashing_spans))]
 		pub fn reap_stash(