Fix E231 false-positive on Python 3.12

Ported PyCQA/pycodestyle#1148

Author: at-wat

src/roslint/pycodestyle.py

@@ -2011,6 +2011,11 @@ def build_tokens_line(self):
                 continue
             if token_type == tokenize.STRING:
                 text = mute_string(text)
+            elif (
+                    sys.version_info >= (3, 12) and
+                    token_type == tokenize.FSTRING_MIDDLE
+            ):
+                text = 'x' * len(text)
             if prev_row:
                 (start_row, start_col) = start
                 if prev_row != start_row:    # different row