Fix typo in link syntax (#315)

Author: Simran-B

index.bs

@@ -6861,7 +6861,7 @@ For the revision history of the second edition, see [that document's Revision Hi
 * Added {{IDBCursor/request}} attribute. ([Issue #255](https://github.com/w3c/IndexedDB/issues/255))
 * Removed handling for nonstandard `lastModifiedDate` property of {{File}} objects. ([Issue #215](https://github.com/w3c/IndexedDB/issues/215))
 * Remove escaping {{IDBKeyRange/includes()}} method. ([Issue #294](https://github.com/w3c/IndexedDB/issues/294))
-* Restrict array keys to [=/Array exotic objects=] (i.e. disallow proxies). ([Issue #309](https://github.com/w3c/IndexedDB/issues/309])
+* Restrict array keys to [=/Array exotic objects=] (i.e. disallow proxies). ([Issue #309](https://github.com/w3c/IndexedDB/issues/309))
 * Transactions are now temporarily made inactive during clone operations.
 * Added {{IDBTransactionOptions/durability}} option and {{IDBTransaction/durability}} attribute. ([Issue #50](https://github.com/w3c/IndexedDB/issues/50))