Update globals.d.ts for Blob.slice() contentType declaration (#38163)

Summary:
For the contentType Parameter of the method slice in Class Blob which was fixed for
#38078
 the typescript declaration is missing.

## Changelog:
[GENERAL] [ADDED] - Added contentType parameter to Blob declaration

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Pull Request resolved: #38163

Test Plan: I ran yarn run test-typescript and check with Webstorm and VSCode.

Reviewed By: rshest

Differential Revision: D47228992

Pulled By: javache

fbshipit-source-id: fd767bb47c5e64657bfafba4c84d1d8671857109

packages/react-native/types/modules/globals.d.ts

@@ -67,7 +67,7 @@ declare interface WindowOrWorkerGlobalScope {
 interface Blob {
   readonly size: number;
   readonly type: string;
-  slice(start?: number, end?: number): Blob;
+  slice(start?: number, end?: number, contentType?: string): Blob;
 }
 
 interface BlobOptions {