chore: fix function name (#2501)

Signed-off-by: zoupingshi <[email protected]>

eth/fetcher/block_fetcher_test.go

@@ -158,7 +158,7 @@ func (f *fetcherTester) chainFinalizedHeight() uint64 {
 	return f.blocks[f.hashes[len(f.hashes)-3]].NumberU64()
 }
 
-// insertChain injects a new headers into the simulated chain.
+// insertHeaders injects a new headers into the simulated chain.
 func (f *fetcherTester) insertHeaders(headers []*types.Header) (int, error) {
 	f.lock.Lock()
 	defer f.lock.Unlock()