fix(gui): metadata generation

Description

This caused failed parsing of the metadata.xml in proxygui_idp.

How to test

See https://perunaai.atlassian.net/wiki/spaces/DEVS/pages/162070538/How+to+test+modifications+to+proxy

Author's checklist

• I have followed the contribution guidelines
• This MR has been tested or does not change functionality
• I have added relevant merge request dependencies (if this MR has any)
• I have added the correct labels
• I have assigned reviewers (if any are relevant)
• I have edited the documentation (if the changes require it) or I have noted the need for the change if I do not have access to the documentation
• I have marked all introduced BREAKING CHANGES or necessary DEPLOYMENT NOTES in the commit message(s)

Reviewer's checklist

• This MR has been tested or does not change functionality
• This MR has correct commit message format

Other information

None

Related issues

re STR-1277