Only rotate the subsection of the Path

Closes matplotlib#27062

The code for rotation had referred to the original path, when it should
only be rotating the connected segment, which had already been
extracted.

Author: ksunden

lib/matplotlib/contour.py

@@ -383,7 +383,7 @@ def _split_path_and_get_label_rotation(self, path, idx, screen_pos, lw, spacing=
         # If the path is closed, rotate it s.t. it starts at the label.
         is_closed_path = codes[stop - 1] == Path.CLOSEPOLY
         if is_closed_path:
-            cc_xys = np.concatenate([xys[idx:-1], xys[:idx+1]])
+            cc_xys = np.concatenate([cc_xys[idx:-1], cc_xys[:idx+1]])
             idx = 0
 
         # Like np.interp, but additionally vectorized over fp.