Fix wording

Author: kgryte

lib/node_modules/@stdlib/iter/dedupe-by/README.md

@@ -76,7 +76,7 @@ The returned [iterator][mdn-iterator-protocol] protocol-compliant object has the
 -   **next**: function which returns an [iterator][mdn-iterator-protocol] protocol-compliant object containing the next iterated value (if one exists) assigned to a `value` property and a `done` property having a `boolean` value indicating whether the [iterator][mdn-iterator-protocol] is finished.
 -   **return**: function which closes an [iterator][mdn-iterator-protocol] and returns a single (optional) argument in an [iterator][mdn-iterator-protocol] protocol-compliant object.
 
-The provided function is provided four arguments:
+The provided function is provided five arguments:
 
 -   **curr**: current source iterated value.
 -   **sprev**: previous source iterated value.