Make evening info less specific (#67)

* Make info less specific

remove reference to "three" open evenings

* remove extra word

_pages/joining.md

@@ -8,7 +8,7 @@ If you’re interested in what we do, get in touch below or just come along and
 
 Drop in anytime to one of our [open evenings](/calendar/) to get a feel of the Hackspace and see how things work.
 
-Joining costs £6 a month for the three sessions a week, or £21 a month for a key, allowing you to come and go as you please.
+Joining costs £6 a month to attend the [open evenings](/calendar/), or £21 a month for a key, allowing you to come and go as you please.
 
 If you have any questions before you come along you can email us at [[email protected]](mailto:[email protected]).