[minor] Fix nit in error message

Closes #2276

Author: lpinca

lib/websocket.js

@@ -708,7 +708,7 @@ function initAsClient(websocket, address, protocols, options) {
   if (parsedUrl.protocol !== 'ws:' && !isSecure && !isIpcUrl) {
     invalidUrlMessage =
       'The URL\'s protocol must be one of "ws:", "wss:", ' +
-      '"http:", "https", or "ws+unix:"';
+      '"http:", "https:", or "ws+unix:"';
   } else if (isIpcUrl && !parsedUrl.pathname) {
     invalidUrlMessage = "The URL's pathname is empty";
   } else if (parsedUrl.hash) {

test/websocket.test.js

@@ -52,7 +52,7 @@ describe('WebSocket', () => {
           assert.strictEqual(
             err.message,
             'The URL\'s protocol must be one of "ws:", "wss:", ' +
-              '"http:", "https", or "ws+unix:"'
+              '"http:", "https:", or "ws+unix:"'
           );
 
           return true;
@@ -1515,7 +1515,7 @@ describe('WebSocket', () => {
         assert.strictEqual(
           err.message,
           'The URL\'s protocol must be one of "ws:", "wss:", ' +
-            '"http:", "https", or "ws+unix:"'
+            '"http:", "https:", or "ws+unix:"'
         );
         assert.strictEqual(ws._redirects, 1);