Added correct diagnostic mode display

Before the patch, the diagnostic mode was displayed as "Not available",
after the patch "Diagnostic mode".

Test: in the console run the command
"busctl set-property xyz.openbmc_project.State.Host \
/xyz/openbmc_project/state/host0 \
xyz.openbmc_project.State.Host CurrentHostState \
s "xyz.openbmc_project.State.Host.HostState.DiagnosticMode".
open the "Server power operations" page,
check the Server status

Signed-off-by: glukhov.mikhail <mikl@greenfil.ru>
Change-Id: I90d04e05188eb92c4c4b38fe578ae36db0424b5c
diff --git a/src/locales/en-US.json b/src/locales/en-US.json
index cc52f26..dd34fbb 100644
--- a/src/locales/en-US.json
+++ b/src/locales/en-US.json
@@ -55,6 +55,7 @@
     },
     "status": {
       "copied": "Copied",
+      "diagnosticMode": "Diagnostic mode",
       "disabled": "Disabled",
       "enabled": "Enabled",
       "error": "Error",