Bug 1742438 - Prep Part 10: Make TriggeringPrincipal optional for ScriptFetchOptions; r=jonco

I didn't realize that this would only be used in the DOM script loader, so this is now optional. In
a later stage we might move this over to the ScriptLoadContext as it looks like this might need to
propogate through the module script tree.

Differential Revision: https://phabricator.services.mozilla.com/D146172

js/loader/ScriptLoadRequest.cpp

@@ -43,9 +43,7 @@ ScriptFetchOptions::ScriptFetchOptions(
     : mCORSMode(aCORSMode),
       mReferrerPolicy(aReferrerPolicy),
       mTriggeringPrincipal(aTriggeringPrincipal),
-      mElement(aElement) {
-  MOZ_ASSERT(mTriggeringPrincipal);
-}
+      mElement(aElement) {}
 
 ScriptFetchOptions::~ScriptFetchOptions() = default;