Bump bootstrap-multiselect from 1.1.0 to 2.0.0 in /gui/admin-gui

Bumps [bootstrap-multiselect](https://github.com/davidstutz/bootstrap-multiselect) from 1.1.0 to 2.0.0.
- [Release notes](https://github.com/davidstutz/bootstrap-multiselect/releases)
- [Commits](davidstutz/bootstrap-multiselect@v1.1.0...v2.0.0)

---
updated-dependencies:
- dependency-name: bootstrap-multiselect
  dependency-version: 2.0.0
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

gui/admin-gui/package-lock.json

@@ -21,7 +21,7 @@
     "ace-builds": "^1.38.0",
     "admin-lte": "3.2.0",
     "babel-loader": "^9.2.1",
-    "bootstrap-multiselect": "^1.1.0",
+    "bootstrap-multiselect": "^2.0.0",
     "bootstrap-select": "^1.13.18",
     "bootstrap4-toggle": "^3.6.1",
     "bs-stepper": "^1.7.0",