Add definition for setPrivacySetting (#40510)

* Add definition for setPrivacySetting

The docs for this addition to gpt can be found here: https://support.google.com/admanager/answer/9598414
Unfortunately the official documentation has not caught up, see here: https://developers.google.com/doubleclick-gpt/reference#googletag.PubAdsService
There doesn't seem to be anything else it takes besides that, based on the above documentation.

* Contribution Addition

types/doubleclick-gpt/index.d.ts

@@ -4,6 +4,7 @@
 //                 Steven Joyce <https://github.com/steven-joyce>
 //                 Joe Flateau <https://github.com/joeflateau>
 //                 Vanessa Garcia <https://github.com/vanessa-lyn>
+//                 Krishna Glick <https://github.com/krishnaglick>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.2
 
@@ -118,6 +119,7 @@ declare namespace googletag {
         setForceSafeFrame(forceSafeFrame: boolean): Slot;
         setSafeFrameConfig(config: SafeFrameConfig): Slot;
         setTargeting(key: string, value: string | string[]): Slot;
+        setPrivacySettings(settings: { restrictDataProcessing: boolean }): Slot;
     }
 
     interface PassbackSlot {