Bump bootstrap from 3.4.1 to 5.3.8

---
updated-dependencies:
- dependency-name: bootstrap
  dependency-version: 5.3.8
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

AIUB Forum API/packages.config

@@ -2,7 +2,7 @@
 <packages>
   <package id="Antlr" version="3.5.0.2" targetFramework="net472" />
   <package id="AutoMapper" version="10.0.0" targetFramework="net472" />
-  <package id="bootstrap" version="3.4.1" targetFramework="net472" />
+  <package id="bootstrap" version="5.3.8" targetFramework="net481" />
   <package id="jQuery" version="3.5.0" targetFramework="net472" />
   <package id="Microsoft.AspNet.Mvc" version="5.3.0" targetFramework="net472" />
   <package id="Microsoft.AspNet.Razor" version="3.3.0" targetFramework="net472" />