DEV: Correct typos and spelling mistakes (#12812)

Over the years we accrued many spelling mistakes in the code base. 

This PR attempts to fix spelling mistakes and typos in all areas of the code that are extremely safe to change 

- comments
- test descriptions
- other low risk areas

spec/requests/session_controller_spec.rb

@@ -495,7 +495,7 @@ RSpec.describe SessionController do
       expect(session[:current_user_id]).to be_blank
     end
 
-    it "works in developmenet mode" do
+    it "works in development mode" do
       Rails.env.stubs(:development?).returns(true)
       get "/session/#{user.username}/become.json"
       expect(response).to be_redirect
@@ -543,7 +543,7 @@ RSpec.describe SessionController do
       sso
     end
 
-    it 'does not create superflous auth tokens when already logged in' do
+    it 'does not create superfluous auth tokens when already logged in' do
       user = Fabricate(:user)
       sign_in(user)
 
@@ -2188,7 +2188,7 @@ RSpec.describe SessionController do
 
   describe '#current' do
     context "when not logged in" do
-      it "retuns 404" do
+      it "returns 404" do
         get "/session/current.json"
         expect(response.status).to eq(404)
       end