Add swapnilgupta@ to OWNERS in subdirs

Add swapnilgupta@ to OWNERS in the following directory:
forced_extensions in chrome/browser/extensions/

Change-Id: I051d997768624f720c7950250b17eb488db62b12
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2364534Reviewed-by: Oleg Davydov <burunduk@chromium.org>
Commit-Queue: Swapnil Gupta <swapnilgupta@google.com>
Cr-Commit-Position: refs/heads/master@{#800537}

chrome/browser/extensions/forced_extensions/OWNERS

@@ -2,5 +2,6 @@ file://extensions/OWNERS
 
 burunduk@chromium.org
 poromov@chromium.org
+swapnilgupta@google.com
 
 # COMPONENT: Platform>Extensions