Fix Slash command templates

These templates were broken, as the same views didn't have a @project
defined. Now I've added checks on the service being a template or not.

Fixes #26042

app/views/projects/services/mattermost_slash_commands/_help.html.haml

@@ -8,8 +8,8 @@
   by entering
   %code /<command_trigger_word> help
 
-  - unless enabled
+  - unless enabled || @service.template?
     = render 'projects/services/mattermost_slash_commands/detailed_help', subject: @service
 
-- if enabled
+- if enabled && !@service.template?
   = render 'projects/services/mattermost_slash_commands/installation_info', subject: @service

app/views/projects/services/slack_slash_commands/_help.html.haml

@@ -1,4 +1,5 @@
-- run_actions_text = "Perform common operations on this project: #{@project.name_with_namespace}"
+- pretty_name = defined?(@project) ? @project.path_with_namespace : "namespace / path"
+- run_actions_text = "Perform common operations on this project: #{pretty_name}"
 
 .well
   This service allows GitLab users to perform common operations on this
@@ -9,6 +10,7 @@
   %code /<command> help
   %br
   %br
+  - unless @service.template?
     To setup this service:
     %ul.list-unstyled
       %li