Fix some typos (#2560)

* Fix some typos

Corect some words for reading more easily

* Update NOERROR response code

NOERROR is a response code so I revert the typo checking for it

plugin/cache/README.md

@@ -19,7 +19,7 @@ cache [TTL] [ZONES...]
 ~~~
 
 * **TTL** max TTL in seconds. If not specified, the maximum TTL will be used, which is 3600 for
-    noerror responses and 1800 for denial of existence ones.
+    NOERROR responses and 1800 for denial of existence ones.
     Setting a TTL of 300: `cache 300` would cache records up to 300 seconds.
 * **ZONES** zones it should cache for. If empty, the zones from the configuration block are used.
 

plugin/cache/cache.go

@@ -118,7 +118,7 @@ type ResponseWriter struct {
 
 // newPrefetchResponseWriter returns a Cache ResponseWriter to be used in
 // prefetch requests. It ensures RemoteAddr() can be called even after the
-// original connetion has already been closed.
+// original connection has already been closed.
 func newPrefetchResponseWriter(server string, state request.Request, c *Cache) *ResponseWriter {
 	// Resolve the address now, the connection might be already closed when the
 	// actual prefetch request is made.