Fix SDK source in CDN bundles

[mydea]

Is there an existing issue for this?

• I have checked for existing issues https://github.com/getsentry/sentry-javascript/issues
• I have reviewed the documentation https://docs.sentry.io/
• I am using the latest SDK release https://github.com/getsentry/sentry-javascript/releases

How do you use Sentry?

Sentry Saas (sentry.io)

Which SDK are you using?

@sentry/browser

SDK Version

8.26.0

Framework Version

No response

Link to Sentry event

No response

Reproduction Example/SDK Setup

No response

Steps to Reproduce

• Look at e.g. https://browser.sentry-cdn.com/8.26.0/bundle.tracing.replay.feedback.js
• Search for function getSDKSource() {
• It is return "npm"

Expected Result

Should return cdn.

Actual Result

Return npm

The problem is that we replace __SENTRY_SDK_SOURCE__ in the utils package already with npm, then we try to replace it again when building the CDN bundles, but at this point the magic string is already gone..

We should probably do this the same way as we do it for the debug flags, where we replace it twice.