Fix checking for changes in untracked files

[thornbill]

Fixes the check for changed files in the unstable branch update action to also consider untracked files

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud