allocatorimpl: remove CountBasedRebalancingOnlyEnabledByMMA

This commit removes `CountBasedRebalancingOnlyEnabledByMMA`, which was left
unused.

Author: wenyihu6

pkg/kv/kvserver/allocator/allocatorimpl/allocator.go

@@ -2818,17 +2818,6 @@ func (a *Allocator) CountBasedRebalancingDisabled() bool {
 	return kvserverbase.LoadBasedRebalancingMode.Get(&a.st.SV) == kvserverbase.LBRebalancingMultiMetricOnly
 }
 
-// CountBasedRebalancingOnlyEnabledByMMA returns true if count-based rebalancing
-// should be enabled only when mma (multi-metric store rebalancer) allows the
-// change. This is used to prevent thrashing when both multi-metric and
-// count-based rebalancing are enabled and have conflicting goals.
-// TODO(wenyihu6): since we sometimes see even worse thrashing behaviour with
-// this change, should we introduce two modes
-// (mma-count with+without thrashing prevention)?
-func (a *Allocator) CountBasedRebalancingOnlyEnabledByMMA() bool {
-	return kvserverbase.LoadBasedRebalancingMode.Get(&a.st.SV) == kvserverbase.LBRebalancingMultiMetricAndCount
-}
-
 // ShouldTransferLease returns true if the specified store is overfull in terms
 // of leases with respect to the other stores matching the specified
 // attributes.

pkg/kv/kvserver/mmaintegration/thrashing.go

@@ -87,8 +87,8 @@ import (
 // passed to IsInConflictWithMMA to determine if a candidate conflicts with
 // MMA's goals.
 //
-// If MMA is disabled, a no-op advisor is returned, which always returns false
-// for IsInConflictWithMMA. If MMA is enabled, the advisor is created by
+// If mma-count is disabled, a no-op advisor is returned, which always returns
+// false for IsInConflictWithMMA. If MMA is enabled, the advisor is created by
 // computing the load summary for the provided existing store and candidate set.
 //
 // Note that MMARebalanceAdvisor should always use the means summary constructed