fixed one grammar error. (#297)

Just a small grammar change in the README.

Reviewed-on: https://codeberg.org/Codeberg/pages-server/pulls/297
Reviewed-by: crapStone <codeberg@crapstone.dev>
Co-authored-by: caelandb <bothacaelan@gmail.com>
Co-committed-by: caelandb <bothacaelan@gmail.com>

README.md

@@ -116,7 +116,7 @@ Thank you very much.
 Make sure you have [golang](https://go.dev) v1.21 or newer and [just](https://just.systems/man/en/) installed.
 
 run `just dev`  
-now this pages should work:
+now these pages should work:
 
 - <https://cb_pages_tests.localhost.mock.directory:4430/images/827679288a.jpg>
 - <https://momar.localhost.mock.directory:4430/ci-testing/>