[misc] Update flake8 to version 7.2.0 and fix its complains

Author: dmitry-kabanov

.pre-commit-config.yaml

@@ -28,7 +28,7 @@ repos:
 
 
     - repo: https://github.com/pycqa/flake8
-      rev: 7.1.2
+      rev: 7.2.0
       hooks:
           - id: flake8
     - repo: https://github.com/psf/black

examples/compare_performance_ivp_burgers_eq.py

@@ -197,7 +197,6 @@ def analyze(tts_list):
 
 
 def _run_once(impl, N=1001, plot_solution=True) -> float:
-    global memory_monitor
     print("================================================================")
     print(f"Solving Burgers' equation with time integration {impl}, N = {N}")
     begin_time = time.time()