Rebaseline test_small_js_flags. NFC

We should really update this test so that it can work with
`--rebaseline`, but for now its just a manual update.

This change shows the incremental progress we've been making on code
size recently!

Author: sbc100

test/test_browser.py

@@ -4204,7 +4204,9 @@ def test_small_js_flags(self):
     print('size:', size)
     # Note that this size includes test harness additions (for reporting the result, etc.).
     if not self.is_wasm64() and not self.is_2gb():
-      self.assertLess(abs(size - 4477), 100)
+      expected_size = 4369
+      slack = 100
+      self.assertLess(abs(size - expected_size), slack)
 
   # Tests that it is possible to initialize and render WebGL content in a
   # pthread by using OffscreenCanvas.