fix(graphcache): mutation would cause dependent operations and reexec…

…uting operations become the same set

The PR urql-graphql#2761 moved `reexecutingOperations = dependentOperations` assignment
into `if (operation.kind === 'query')` guard. Thus after a completion of
mutation, `dependentOperations = _reexecutingOperations` make reexecuting and
dependent operations the same set object.

exchanges/graphcache/src/cacheExchange.ts

@@ -136,8 +136,9 @@ export const cacheExchange =
         // Upon completion, all dependent operations become reexecuting operations, preventing
         // them from reexecuting prior operations again, causing infinite loops
         const _reexecutingOperations = reexecutingOperations;
+        reexecutingOperations = dependentOperations;
         if (operation.kind === 'query') {
-          (reexecutingOperations = dependentOperations).add(operation.key);
+          reexecutingOperations.add(operation.key);
         }
         (dependentOperations = _reexecutingOperations).clear();
       }