[minor] Use Buffer#subarray() instead of Buffer#slice()

`Buffer.prototype.slice()` is deprecated.

Author: lpinca

lib/buffer-util.js

@@ -23,7 +23,7 @@ function concat(list, totalLength) {
     offset += buf.length;
   }
 
-  if (offset < totalLength) return target.slice(0, offset);
+  if (offset < totalLength) return target.subarray(0, offset);
 
   return target;
 }

lib/permessage-deflate.js

@@ -437,7 +437,7 @@ class PerMessageDeflate {
         this._deflate[kTotalLength]
       );
 
-      if (fin) data = data.slice(0, data.length - 4);
+      if (fin) data = data.subarray(0, data.length - 4);
 
       //
       // Ensure that the callback will not be called again in

lib/receiver.js

@@ -97,8 +97,8 @@ class Receiver extends Writable {
 
     if (n < this._buffers[0].length) {
       const buf = this._buffers[0];
-      this._buffers[0] = buf.slice(n);
-      return buf.slice(0, n);
+      this._buffers[0] = buf.subarray(n);
+      return buf.subarray(0, n);
     }
 
     const dst = Buffer.allocUnsafe(n);
@@ -111,7 +111,7 @@ class Receiver extends Writable {
         dst.set(this._buffers.shift(), offset);
       } else {
         dst.set(new Uint8Array(buf.buffer, buf.byteOffset, n), offset);
-        this._buffers[0] = buf.slice(n);
+        this._buffers[0] = buf.subarray(n);
       }
 
       n -= buf.length;
@@ -562,7 +562,7 @@ class Receiver extends Writable {
           );
         }
 
-        const buf = data.slice(2);
+        const buf = data.subarray(2);
 
         if (!this._skipUTF8Validation && !isValidUTF8(buf)) {
           return error(