fixup! Improve the _select module description

Author: llucax

src/frequenz/channels/_select.py

@@ -13,7 +13,7 @@
 receivers as they receive new values.
 
 It yields a [`Selected`][frequenz.channels.Selected] object that will tell you the
-source of the received message. To make sure the received value is *casted* to the
+source of the received message. To make sure the received value is *cast* to the
 correct type, you need to use the [`selected_from()`][frequenz.channels.selected_from]
 function to check the source of the message, and the
 [`value`][frequenz.channels.Selected.value] attribute to access the message: