test: update Safari 15 private property E2E for babel changes

Recent babel downlevelling changes for private properties require
adjustments to the test expectations for the `misc/safari-15-class-properties`
E2E test. This E2E test ensured that private class properties are
downlevelled when Safari 15 is present in the supported browsers list
to workaround Safari bugs that were present in these older versions of
the browser.

(cherry picked from commit 1ae6252)

Author: clydin

Diff for: tests/legacy-cli/e2e/tests/misc/safari-15-class-properties.ts

@@ -1,6 +1,7 @@
 import assert from 'node:assert';
 import { expectFileToExist, readFile, writeFile, replaceInFile } from '../../utils/fs';
 import { ng } from '../../utils/process';
+import { getGlobalVariable } from '../../utils/env';
 
 const unexpectedStaticFieldErrorMessage =
   'Found unexpected static field. This indicates that the Safari <=v15 ' +
@@ -55,9 +56,17 @@ export default async function () {
     unexpectedStaticFieldErrorMessage,
   );
 
-  assert.match(
-    mainContentSafari15Explicit,
-    /var _myPrivateMethod/,
-    'Expected private method to be downlevelled when Safari <=v15 is targeted',
-  );
+  if (getGlobalVariable('argv')['esbuild']) {
+    assert.match(
+      mainContentSafari15Explicit,
+      /var _myPrivateMethod/,
+      'Expected private method to be downlevelled when Safari <=v15 is targeted',
+    );
+  } else {
+    assert.match(
+      mainContentSafari15Explicit,
+      /_assertClassBrand/,
+      'Expected private method to be downlevelled when Safari <=v15 is targeted',
+    );
+  }
 }