Partial rollback of

3aea836

*** Reason for rollback ***

This is no longer necessary now that we calculate side effects correctly for 'await' nodes.

*** Original change description ***

Don't remove unused 'await' expressions

***

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=176433132

src/com/google/javascript/jscomp/PeepholeRemoveDeadCode.java

@@ -260,10 +260,6 @@ private Node trySimplifyUnusedResult(Node n, boolean removeUnused) {
           result = n;
         }
         break;
-      case AWAIT:
-        // If there's an 'await' node whose result isn't used, it's still important to wait
-        // for the promise to resolve before running the next line, so don't remove it.
-        break;
       default:
         if (!nodeTypeMayHaveSideEffects(n)) {
           // This is the meat of this function. The node itself doesn't generate