[mv3] Remove obsolete Firefox-only workaround in scriptlet template

Related bugzilla issue:
https://bugzilla.mozilla.org/show_bug.cgi?id=1736575

The issue was fixed months ago.

The removed code block is causing uBOL to be flagged as "including
remotely hosted code".

To be clear, the removed obsolete code block was not related to
executing remote code. The referenced code was in the file itself,
not remote, and this was a workaround for when Firefox was not
supporting injecting script in the `MAIN` world.

The issue was fixed months ago in Firefox, so there is no point for
the workaround.

platform/mv3/scriptlets/scriptlet.template.js

@@ -21,7 +21,6 @@
 */
 
 /* eslint-disable indent */
-/* global cloneInto */
 
 // ruleset: $rulesetId$
 
@@ -136,44 +135,7 @@ argsList.length = 0;
 
 /******************************************************************************/
 
-// Inject code
-
-// https://bugzilla.mozilla.org/show_bug.cgi?id=1736575
-//   'MAIN' world not yet supported in Firefox, so we inject the code into
-//   'MAIN' ourself when environment in Firefox.
-
-const targetWorld = '$world$';
-
-// Not Firefox
-if ( typeof wrappedJSObject !== 'object' || targetWorld === 'ISOLATED' ) {
-    return uBOL_$scriptletName$();
-}
-
-// Firefox
-{
-    const page = self.wrappedJSObject;
-    let script, url;
-    try {
-        page.uBOL_$scriptletName$ = cloneInto([
-            [ '(', uBOL_$scriptletName$.toString(), ')();' ],
-            { type: 'text/javascript; charset=utf-8' },
-        ], self);
-        const blob = new page.Blob(...page.uBOL_$scriptletName$);
-        url = page.URL.createObjectURL(blob);
-        const doc = page.document;
-        script = doc.createElement('script');
-        script.async = false;
-        script.src = url;
-        (doc.head || doc.documentElement || doc).append(script);
-    } catch (ex) {
-        console.error(ex);
-    }
-    if ( url ) {
-        if ( script ) { script.remove(); }
-        page.URL.revokeObjectURL(url);
-    }
-    delete page.uBOL_$scriptletName$;
-}
+uBOL_$scriptletName$();
 
 /******************************************************************************/