chore(sveltekit): Use dummy DSN var in README instructions (#7521)

Author: AbhiPrasad

packages/sveltekit/README.md

@@ -54,7 +54,7 @@ Although the SDK is not yet stable, you're more than welcome to give it a try an
     import * as Sentry from '@sentry/sveltekit';
 
     Sentry.init({
-      dsn: 'https://[email protected]/4504796902588416',
+      dsn: '__DSN__',
 
       // For instance, initialize Session Replay:
       replaysSessionSampleRate: 0.1,
@@ -81,7 +81,7 @@ Although the SDK is not yet stable, you're more than welcome to give it a try an
     import * as Sentry from '@sentry/sveltekit';
 
     Sentry.init({
-      dsn: 'https://[email protected]/4504796902588416',
+      dsn: '__DSN__',
     });
    ```