DevTools: [CSS] remove getAllStylesheets method from protocol

Source/devtools/protocol.json

 {
     "version": { "major": "1", "minor": "1" },
     "domains": [{
         "domain": "Inspector",
         "hidden": true,
         "types": [],
         "commands": [
             {
                 "name": "enable",
                 "description": "Enables inspector domain notifications."
@@ skipping 2652 matching lines @@
                     { "name": "nodeId", "$ref": "DOM.NodeId" }
                 ],
                 "returns": [
                     { "name": "cssFamilyName", "type": "string", "description": "Font family name which is determined by computed style." },
                     { "name": "fonts", "type": "array", "items": { "$ref": "PlatformFontUsage" }, "description": "Usage statistics for every employed platform font." }
                 ],
                 "description": "Requests information about platform fonts which we used to render child TextNodes in the given node.",
                 "hidden": true
             },
             {
-                "name": "getAllStyleSheets",
-                "returns": [
-                    { "name": "headers", "type": "array", "items": { "$ref": "CSSStyleSheetHeader" }, "description": "Descriptor entries for all available stylesheets." }
-                ],
-                "description": "Returns metainfo entries for all known stylesheets."
-            },
-            {
                 "name": "getStyleSheet",
                 "parameters": [
                     { "name": "styleSheetId", "$ref": "StyleSheetId" }
                 ],
                 "returns": [
                     { "name": "styleSheet", "$ref": "CSSStyleSheetBody", "description": "Stylesheet contents for the specified <code>styleSheetId</code>." }
                 ],
                 "description": "Returns stylesheet data for the specified <code>styleSheetId</code>."
             },
             {
@@ skipping 1455 matching lines @@
                 ],
                 "handlers": ["browser", "frontend"]
             },
             {
                 "name": "tracingComplete",
                 "handlers": ["browser", "frontend"]
             }
         ]
     }]
 }