docs: update readme cache instructions

Swapped the npm cache verify around (line 130). Commented out the npm cache clean for npm version older than 5.

Author: estrellajm

README.md

@@ -127,8 +127,8 @@ To update Angular CLI to a new version, you must update both the global package
 Global package:
 ```bash
 npm uninstall -g @angular/cli
-npm cache clean
-# if npm version is > 5 then use `npm cache verify` to avoid errors (or to avoid using --force)
+npm cache verify
+# if npm version is < 5 the use `npm cache clean`
 npm install -g @angular/cli@latest
 ```