The .encode("utf-8") fixer generates wrong code

[svenpanne]

Repro: Add the following test:

diff --git a/tests/features/default_encoding_test.py b/tests/features/default_encoding_test.py
index f039fdc..6fb1277 100644
--- a/tests/features/default_encoding_test.py
+++ b/tests/features/default_encoding_test.py
@@ -38,6 +38,11 @@ from pyupgrade._main import _fix_plugins
             'f"{x}(".encode()',
             id='3.12+ handle open brace in fstring',
         ),
+        pytest.param(
+            'f"{foo(bar)}(".encode("utf-8")',
+            'f"{foo(bar)}(".encode()',
+            id='f-string with function call',
+        ),
     ),
 )
 def test_fix_encode(s, expected):

The corresponding test will then fail with:

...
>       assert ret == expected
E       assert 'f"{foo()}(".encode("utf-8")' == 'f"{foo(bar)}(".encode()'
E         
E         - f"{foo(bar)}(".encode()
E         ?        ---
E         + f"{foo()}(".encode("utf-8")
E         ?                    +++++++

tests/features/default_encoding_test.py:50: AssertionError

i.e. the fixer doesn't remove the "utf-8" literal, it removes the argument of another function call-