CommitteeCache.get_all_beacon_committees: set correct capacity to avo…

…id realloc (sigp#4557)

consensus/types/src/beacon_state/committee_cache.rs

@@ -174,7 +174,7 @@ impl CommitteeCache {
  .ok_or(Error::CommitteeCacheUninitialized(None))?;
 
  initialized_epoch.slot_iter(self.slots_per_epoch).try_fold(
- Vec::with_capacity(self.slots_per_epoch as usize),
+ Vec::with_capacity(self.epoch_committee_count()),
  |mut vec, slot| {
  vec.append(&mut self.get_beacon_committees_at_slot(slot)?);
  Ok(vec)