init: fix snake case linting

src/amdgpu_stats/__init__.py

@@ -20,7 +20,7 @@ def check_for_cards() -> bool:
 def textual_run() -> None:
     """runs the AMD GPU Stats TUI; called only when in an interactive shell"""
     if check_for_cards():
-        AMDGPUStats = app(watch_css=True)
-        AMDGPUStats.run()
+        amdgpu_stats_app = app(watch_css=True)
+        amdgpu_stats_app.run()
     else:
         sys.exit('Could not find an AMD GPU, exiting.')