GUACAMOLE-815: Remove duplicated "timezone" field definitions and translations.

guacamole/src/main/webapp/translations/en.json

@@ -415,7 +415,6 @@
         "FIELD_HEADER_REMOTE_APP_ARGS" : "Parameters:",
         "FIELD_HEADER_REMOTE_APP_DIR"  : "Working directory:",
         "FIELD_HEADER_REMOTE_APP"      : "Program:",
-        "FIELD_HEADER_TIMEZONE"        : "Timezone:",
         "FIELD_HEADER_SECURITY"        : "Security mode:",
         "FIELD_HEADER_SERVER_LAYOUT"   : "Keyboard layout:",
         "FIELD_HEADER_SFTP_DIRECTORY"             : "Default upload directory:",