Fix Template.latest_version ambiguity error

- Prior to this commit, the following error was encountered when applying the search filter within `/org_admin/templates`:

```
ActiveRecord::StatementInvalid - PG::AmbiguousColumn: ERROR:  column reference "id" is ambiguous
LINE 1: SELECT COUNT(DISTINCT id) FROM (SELECT MAX(version) AS versi...
                              ^:
  app/views/layouts/_paginable.html.erb:5
  app/controllers/concerns/paginable.rb:82:in `paginable_renderise'
  app/controllers/paginable/templates_controller.rb:25:in `index'
```

- Tracing the code reveals that the query encountering this error is `Template.includes(:org).latest_version.where(customization_of: nil).distinct.total_count`.

- Although `SELECT "templates.*"` is the default behaviour of the `.latest_version` scope, the ambiguity error is raised unless `.select('templates.*')` is added explicitly.

app/models/template.rb

@@ -136,6 +136,10 @@ class Template < ApplicationRecord
                   AND current.family_id = templates.family_id
                 INNER JOIN orgs ON orgs.id = templates.org_id
               SQL
+              # `SELECT "templates.*"` is this scope's default behavior, but it must be explicitly
+              # specified to prevent `PG::AmbiguousColumn` errors when `.distinct.total_count` is used
+              # (e.g. in `app/views/layouts/_paginable.html.erb`)
+              .select('templates.*')
   }
 
   # Retrieves the latest customized versions, i.e. those with maximum version