Update text assertions to be case insensitive

Fixes #6786

With this new version, devise errors
are now lowercase. To prevent these tests
to erroring out again because of uppercase changes,
the text are asserted against a case insensitive
regex.

Author: stefannibrasil

spec/system/all_casa_admins/sessions/new_spec.rb

@@ -53,7 +53,7 @@
         click_on "Log in"
       end
 
-      expect(page).to have_text "Invalid Email or password"
+      expect(page).to have_text(/invalid email or password/i)
     end
 
     it "denies access to flipper" do

spec/system/sessions/login_spec.rb

@@ -23,7 +23,7 @@
         find("#log-in").click
       end
 
-      expect(page).to have_content("Invalid Email or password.")
+      expect(page).to have_content(/invalid email or password/i)
     end
   end
 end

spec/system/sessions/new_spec.rb

@@ -62,7 +62,7 @@
         find("#log-in").click
       end
 
-      expect(page).to have_text "Invalid Email or password"
+      expect(page).to have_text(/invalid email or password/i)
     end
   end