#8238 Unsaved map confirmation zIndex

[belom88]

Description

Fix zIndex value for unsaved map confirmation dialog.

Please check if the PR fulfills these requirements

• [X] The commit message follows our guidelines: https://github.com/geosolutions-it/MapStore2/blob/master/CONTRIBUTING.md
• [ ] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x", remove the others)

• [X] Bugfix
• [ ] Feature
• [ ] Code style update (formatting, local variables)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] CI related changes
• [ ] Other... Please describe:

Issue

#8238

What is the new behavior? Works as expected

Breaking change

Does this PR introduce a breaking change? (check one with "x", remove the other)

• [ ] Yes, and I documented them in migration notes
• [x] No

Other useful information

Reproducible only on https://qa-mapstore.geosolutionsgroup.com/mapstore/#/