all: fix spelling mistakes (#25961)

eth/downloader/queue.go

@@ -632,7 +632,7 @@ func (q *queue) ExpireReceipts(peer string) int {
 // lock is not obtained in here is that the parameters already need to access
 // the queue, so they already need a lock anyway.
 func (q *queue) expire(peer string, pendPool map[string]*fetchRequest, taskQueue *prque.Prque) int {
-	// Retrieve the request being expired and log an error if it's non-existnet,
+	// Retrieve the request being expired and log an error if it's non-existent,
 	// as there's no order of events that should lead to such expirations.
 	req := pendPool[peer]
 	if req == nil {

eth/downloader/skeleton.go

@@ -35,7 +35,7 @@ import (
 // scratchHeaders is the number of headers to store in a scratch space to allow
 // concurrent downloads. A header is about 0.5KB in size, so there is no worry
 // about using too much memory. The only catch is that we can only validate gaps
-// afer they're linked to the head, so the bigger the scratch space, the larger
+// after they're linked to the head, so the bigger the scratch space, the larger
 // potential for invalid headers.
 //
 // The current scratch space of 131072 headers is expected to use 64MB RAM.