docs(website): use "a" instead of "the"

Here, because we're not referring to a specific table row but instead to _an arbitrary_ table row, we use the indefinite article "a".

Author: TurekBot

src/docs/handbook/web-testing/page-element-query-language.md

@@ -595,7 +595,7 @@ Serenity/JS provides a number of meta-questions, like [`Text`](/api/web/class/Te
 and you can always write your own if needed.
 
 For example, if you're dealing with a web interface that presents tabular data, 
-you might want to fetch the table row, perform some transformation on each cell,
+you might want to fetch a table row, perform some transformation on each cell,
 then return the result as a JSON object so that it's easier to work with.
 
 An equivalent of doing that in our example would be to: