fix(react): remove unnecessary custom GA script validation

Author: ruifcnunes

packages/react/src/analytics/integrations/GA4/GA4.js

@@ -670,12 +670,6 @@ class GA4 extends integrations.Integration {
    * Method that will be called when the GA4 script loads.
    */
   scriptOnload = () => {
-    if (!window.gtag && !!this.customLoadScriptFn) {
-      throw new Error(
-        `${MESSAGE_PREFIX}${INIT_ERROR} Custom load script function finished but 'window.gtag' is not defined.`,
-      );
-    }
-
     if (this.initializePromiseResolve) {
       this.initializePromiseResolve();
       this.initializePromiseResolve = null;

packages/react/src/analytics/integrations/__tests__/GA4.test.js

@@ -150,21 +150,6 @@ describe('GA4 Integration', () => {
           );
         }
       });
-
-      it('Should throw if custom script did not instantiate gtag properly', () => {
-        const options = {
-          ...validOptions,
-          [OPTION_LOAD_SCRIPT_FUNCTION]: () => Promise.resolve(),
-        };
-
-        try {
-          ga4Instance = createGA4Instance(options);
-        } catch (e) {
-          expect(e.message).toContain(
-            `${MESSAGE_PREFIX}${INIT_ERROR}Custom load script function finished but 'window.gtag' is not defined.`,
-          );
-        }
-      });
     });
 
     it('Should throw when tracking event if gtag is not defined', async () => {