Use twentythirteen for this test

Astra requires at least WordPress 5.3 so this test no longer applies
since we flag the update as unavailable. Switch to twentythirteen which
has lower WP requriements and is better to use for testing old versions

Author: mrsdizzie

features/theme.feature

@@ -210,16 +210,16 @@ Feature: Manage WordPress themes
   Scenario: Flag `--skip-update-check` skips update check when running `wp theme list`
     Given a WP install
 
-    When I run `wp theme install astra --version=1.0.0`
+    When I run `wp theme install twentythirteen --version=1.1`
     Then STDOUT should contain:
       """
       Theme installed successfully.
       """
 
     When I run `wp theme list --fields=name,status,update`
     Then STDOUT should be a table containing rows:
-      | name  | status   | update    |
-      | astra | inactive | available |
+      | name           | status   | update    |
+      | twentythirteen | inactive | available |
 
     When I run `wp transient delete update_themes --network`
     Then STDOUT should be:
@@ -229,8 +229,8 @@ Feature: Manage WordPress themes
 
     When I run `wp theme list --fields=name,status,update --skip-update-check`
     Then STDOUT should be a table containing rows:
-      | name  | status   | update |
-      | astra | inactive | none   |
+      | name           | status   | update |
+      | twentythirteen | inactive | none   |
 
   Scenario: Install a theme when the theme directory doesn't yet exist
     Given a WP install