Internal: Translation contexts. (skip ci)

lang/contexts.json

@@ -5,6 +5,6 @@
 	"Edit link": "Button opening the Link URL editing balloon.",
 	"Open link in new tab": "Button opening the link in new browser tab.",
 	"This link has no URL": "Label explaining that a link has no URL set (the URL is empty).",
-	"Open link in a new tab": "The label of the switch button that controls whether the edited link will open in a new tab.",
+	"Open in a new tab": "The label of the switch button that controls whether the edited link will open in a new tab.",
 	"Downloadable": "The label of the switch button that controls whether the edited link refers to downloadable resource."
 }