Apply ruff/flake8-simplify rule SIM201

SIM201 Use `... != ...` instead of `not ... == ...`

Author: DimitriPapadopoulos

src/cffi/verifier.py

@@ -182,7 +182,7 @@ def _write_source(self, file=None):
             # Determine if this matches the current file
             if os.path.exists(self.sourcefilename):
                 with open(self.sourcefilename, "r") as fp:
-                    needs_written = not (fp.read() == source_data)
+                    needs_written = fp.read() != source_data
             else:
                 needs_written = True