Bug 32212: (bug 32030 follow-up) Restore bootstrap 4

During the development of the eRM module I've tried to use bootstrap 5
(and vue-bootstrap), but I didn't manage to make it work without
modifying the version used in Koha. This change is actually not needed
and we can keep version 4.
See commit 8c32f186d5
Bug 32030: ERM - Remove BootstrapVue3

Test plan:
% yarn install
% git diff
you should notice the version change in yarn.lock

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>

package.json

@@ -15,8 +15,7 @@
     "@popperjs/core": "^2.11.2",
     "@vue/cli-service": "^5.0.1",
     "babel-core": "^7.0.0-beta.3",
-    "bootstrap": "^5.1.3",
-    "bootstrap-vue-3": "^0.1.7",
+    "bootstrap": "^4.5.2",
     "css-loader": "^6.6.0",
     "cypress": "^9.5.2",
     "gulp": "^4.0.2",