fix(lockfile): use public Yarn CDN URL for widget-sdk 3.18.0

The resolved URL was 'npm.pkg.github.com/download/...' because the lockfile
was generated with local ~/.npmrc @Staffbase:registry=https://npm.pkg.github.com
active. Yarn classic --frozen-lockfile downloads from the resolved URL directly
so CI got 401. widget-sdk 3.18.0 is on public npmjs.org (same tarball),
so pointing at the Yarn CDN URL needs no auth in CI.

Co-authored-by: GitHub Copilot <copilot@noreply.github.com>

Author: maximizeIT

samples/weather-forecast/yarn.lock

@@ -2534,7 +2534,7 @@
 
 "@staffbase/widget-sdk@^3.18.0":
   version "3.18.0"
-  resolved "https://npm.pkg.github.com/download/@Staffbase/widget-sdk/3.18.0/a2cc04cdce8c21b98f007587ee40fcd18d652c54#a2cc04cdce8c21b98f007587ee40fcd18d652c54"
+  resolved "https://registry.yarnpkg.com/@staffbase/widget-sdk/-/widget-sdk-3.18.0.tgz#a2cc04cdce8c21b98f007587ee40fcd18d652c54"
   integrity sha512-NPRtqe63UhEpCDVaAqOP3xJp+MWHkXw0IHGuiC5JLhd7S5Wiuv/c1Ad+miiKUrx3piJoSBr9elOH5QSy8TU9xg==
   dependencies:
     "@rjsf/core" "^6.3.1"