Remove `maxlength` limit from the project description textarea

In the `General Settings` page one can add an optional project
description. Previously, this textarea field was set to a maximum of
250 characters. In this commit we have remove that limit.

There is an actual limit of 2000 imposed by the backend. If one tries to
save a project description longer than 2000 characters a warning will
appear after clicking `Save changes`.

Changelog: other

app/views/projects/settings/_general.html.haml

@@ -23,7 +23,7 @@
     .row
       .form-group.col-md-9
         = f.label :description, _('Project description (optional)'), class: 'label-bold'
-        = f.text_area :description, class: 'form-control gl-form-input', rows: 3, maxlength: 250
+        = f.text_area :description, class: 'form-control gl-form-input', rows: 3
 
   .row= render_if_exists 'projects/classification_policy_settings', f: f