Bump bootstrap from 4.1.3 to 4.3.1 in /Doctor

Bumps bootstrap from 4.1.3 to 4.3.1.

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

Author: dependabot[bot]

Doctor/packages.config

@@ -2,7 +2,7 @@
 <packages>
   <package id="angularjs" version="1.7.2" targetFramework="net461" />
   <package id="Antlr" version="3.5.0.2" targetFramework="net461" />
-  <package id="bootstrap" version="4.1.3" targetFramework="net461" />
+  <package id="bootstrap" version="4.3.1" targetFramework="net461" />
   <package id="EntityFramework" version="6.2.0" targetFramework="net461" />
   <package id="jQuery" version="3.3.1" targetFramework="net461" />
   <package id="jQuery.Validation" version="1.17.0" targetFramework="net461" />