Update maps.md

Author: ivan-mashonskiy

_overviews/collections-2.13/maps.md

@@ -64,7 +64,7 @@ Mutable maps support in addition the operations summarized in the following tabl
 |  **Additions and Updates:** |                                               |
 |  `ms(k) = v`                |(Or, written out, `ms.update(k, v)`). Adds mapping from key `k` to value `v` to map ms as a side effect, overwriting any previous mapping of `k`.|
 |  `ms.addOne(k -> v)`<br>or `ms += (k -> v)`     |Adds mapping from key `k` to value `v` to map `ms` as a side effect and returns `ms` itself.|
-|  `ms.addAll(xvs)`<br>or `ms ++= kvs`             |Adds all mappings in `kvs` to `ms` as a side effect and returns `ms` itself.|
+|  `ms.addAll(kvs)`<br>or `ms ++= kvs`             |Adds all mappings in `kvs` to `ms` as a side effect and returns `ms` itself.|
 |  `ms.put(k, v)`             |Adds mapping from key `k` to value `v` to `ms` and returns any value previously associated with `k` as an option.|
 |  `ms.getOrElseUpdate(k, d)` |If key `k` is defined in map `ms`, return its associated value. Otherwise, update `ms` with the mapping `k -> d` and return `d`.|
 |  **Removals:**              |                                                |