Fixes simple browser icons are broken in firefox

[jeanp413]

Not a CSP expert but firefox doesn't like the full URL for font-src

<meta
http-equiv="Content-Security-Policy"
content="default-src 'none';
	font-src https://55582f46-d0e8-47cd-9fee-99526b57ac58.vscode-webview-test.com/0d728c31ebdf03869d2687d9be0b017667c9ff37/vscode-resource/http//localhost%3A8080/static/extensions/simple-browser/media/codicon.ttf;
	style-src https://*.vscode-webview-test.com;
	script-src 'nonce-1617229294534534';
	frame-src *;
">

This PR fixes #120036

[mjbvz]

Thanks!