Change comment wording

Co-authored-by: Karl Bartel <[email protected]>

internal/celoapi/backend.go

@@ -26,9 +26,9 @@ func NewCeloBackend(b ethapi.Backend) *CeloBackend {
 // having to change their call signature significantly.
 // CeloBackend keeps a threadsafe LRU cache of block-hash to exchange rates for that block.
 // Cache invalidation is only a problem when an already existing blocks' hash
-// doesn't change, but the rates change. That shouldn't be possible, since changing the rates
+// doesn't change, but the rates change. That isn't possible, since changing the rates
 // requires different transaction hashes / state and thus a different block hash.
-// If the previous rates change during a reorg, the previous block hash should also change
+// If the previous rates change during a reorg, the previous block hash will also change
 // and with it the new block's hash.
 // Stale branches cache values will get evicted eventually.
 type CeloBackend struct {