Use LANGUAGE instead of LC_ALL in fcitx5-diagnose (#1233)

The "locale" command output is very important and we shouldn't let user override it.

Author: wengxt

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -32,6 +32,6 @@ body:
     id: diagnose
     attributes:
       label: Output of fcitx5-diagnose command
-      description: Please copy-paste the output of `LC_ALL=C fcitx5-diagnose` command. If your issue is related to certain application (e.g. cannot use fcitx in some application), please make sure you run this command while this application is running.
+      description: Please copy-paste the output of `LANGUAGE=en fcitx5-diagnose` command. If your issue is related to certain application (e.g. cannot use fcitx in some application), please make sure you run this command while this application is running.
     validations:
       required: true