Include correct CSS file for xterm in environments page

When the xterm dependency was moved to a npm dependency
the CSS file path was not updated correctly in the environments page.

In order for xterm to render properly, it needs the correct CSS path.

app/views/projects/environments/terminal.html.haml

@@ -2,7 +2,7 @@
 - page_title "Terminal for environment", @environment.name
 - content_for :page_specific_javascripts do
-  = stylesheet_link_tag "xterm/xterm"
+  = stylesheet_link_tag "xterm.css"
 %div{ class: container_class }
   .top-area

changelogs/unreleased/50956-web-terminal.yml

+---
+title: Include correct CSS file for xterm in environments page
+merge_request:
+author:
+type: fixed