Try getting sandbox page text again

On CI now the sandbox test is failing on windows when we pop the header
line with an index error. It looks like the only line present on the
page is "Sandbox Status". It was working on CI the other day! Grrr

Hopefully it's a timing issue and the JS just hasn't finished running
yet? Not sure if just loading it again is the most reliable. Ideally we
would be listening for some event...

Pretty low effort but if this makes the test stop being flaky and we
don't have to look at it again that's fine with me.

tests/end2end/test_invocations.py

@@ -883,6 +883,11 @@ def test_sandboxing(
         line.expected = True
         pytest.skip("chrome://sandbox/ not supported")
 
+    if len(text.split("\n")) == 1:
+        # Try again, maybe the JS hasn't run yet?
+        text = quteproc_new.get_content()
+        print(text)
+
     bpf_text = "Seccomp-BPF sandbox"
     yama_text = "Ptrace Protection with Yama LSM"