style: fix remaining E402 import linting error for ast

Author: TasfinMahmud

end_to_end_figures.py

@@ -55,7 +55,7 @@
 
 plt.figure(figsize=(8, 4))
 plt.plot(freqs, mag, color='purple', alpha=0.7)
-import ast
+import ast  # noqa: E402
 import textwrap  # noqa: E402
 
 cause_str = str(diag['root_cause'])