Remove unused flags images

[aduth]

🛠 Summary of changes

Removes two unused flags images.

We use a flags sprite for the phone input component, but it is loaded directly from the node_modules package using the asset pipeline:

identity-idp/config/initializers/assets.rb

Lines 8 to 10 in f00bb67

	# Add additional assets to the asset load path
	Rails.application.config.assets.paths.push(
	'node_modules/intl-tel-input/build/img',

See also:

• Built package assets
• Code reference to sprite

The directory name is also not correct, since the package we use is intl-tel-input, not intl-tel-number.

📜 Testing Plan

Verify there is no regression in the appearance of flags in the phone input component:

1. Go to http://localhost:3000
2. Sign in
3. Click "Add a phone number" from your account dashboard
4. (Reauthenticate if prompted)
5. Verify the phone input shows country flags in the dropdown

👀 Screenshots

There are no visual changes, but here's the phone dropdown after these changes as verification that there is no regression: