Upgrade Bootstrap to 5.3.3

Also switching to sassc-rails as it's the RoR default now and dropping
bootstrap-switch-rails, bootstrap 5 includes switches.

Gemfile.lock

@@ -95,10 +95,9 @@ GEM
     bcrypt (3.1.20)
     bigdecimal (3.1.8)
     bindex (0.8.1)
-    bootstrap-sass (3.4.1)
-      autoprefixer-rails (>= 5.2.1)
-      sassc (>= 2.0.0)
-    bootstrap-switch-rails (3.3.3)
+    bootstrap (5.3.3)
+      autoprefixer-rails (>= 9.1.0)
+      popper_js (>= 2.11.8, < 3)
     builder (3.2.4)
     byebug (11.1.3)
     cancancan (3.6.1)
@@ -368,6 +367,7 @@ GEM
       ruby-rc4
       ttfunk
     pg (1.5.6)
+    popper_js (2.11.8)
     prawn (2.5.0)
       matrix (~> 0.4)
       pdf-core (~> 0.10.0)
@@ -610,10 +610,8 @@ DEPENDENCIES
   acts_as_commentable_with_threading
   acts_as_list
   ajax-datatables-rails
-  autoprefixer-rails
   awesome_nested_set
-  bootstrap-sass (~> 3.4.0)
-  bootstrap-switch-rails (= 3.3.3)
+  bootstrap (~> 5)
   byebug
   cancancan
   capybara
@@ -685,7 +683,7 @@ DEPENDENCIES
   rubocop-rails
   rubocop-rspec
   ruby-oembed
-  sass-rails (>= 4.0.2)
+  sassc-rails
   selectize-rails
   sentry-rails
   shoulda-matchers