Remove references to or invocations of vulcanize.py. It's deleted.

docs/optimizing_web_uis.md

 # Optimizing Chrome Web UIs
 
 ## How do I do it?
 
 In order to build with a fast configuration, try setting these options in your
 GN args:
 
 ```
 use_vulcanize = true
 is_debug = false
 ```
 
-If you make local changes, you likely need to re-run:
-
-```
-$ chrome/browser/resources/vulcanize.py
-```
-
-And rebuild Chrome to see effects. vulcanize.py will result in local changes to
-*crisper* and *vulcanized* files that you must currently check in.
-
-*NOTE: Vuclanize is being integrated directly into
-[GN/Ninja](https://crbug.com/673825), so this workflow is likely to change
-soon.*
-
 ## How is the code optimized?
 
 ### Resource combination
 
 [HTML imports](https://www.html5rocks.com/en/tutorials/webcomponents/imports/)
 are a swell technology, but can be used is slow ways.  Each import may also
 contain additional imports, which must be satisfied before certain things can
 continue (i.e. script execution may be paused).
 
 ```html
@@ skipping 94 matching lines @@
 
 To mark a WebUI's resources compressed, you'll need to do something like:
 
 ```c++
 WebUIDataSource* data_source = WebUIDataSource::Create(...);
 data_source->SetDefaultResource(IDR_MY_PAGE);
 std::unordered_set<std::string> exclusions;
 exclusions.insert("strings.js");  // if required
 data_source->UseGzip(exclusions);
 ```