tools: Python lint fix

Change-Id: If7c41be024774bc32299604b1177148c1ff434df
Reviewed-on: https://pigweed-review.googlesource.com/c/gonk/+/222598
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Commit-Queue: Anthony DiGirolamo <tonymd@google.com>
Reviewed-by: Keir Mierle <keir@google.com>
diff --git a/tools/gonk_tools/plot.py b/tools/gonk_tools/plot.py
index 1306e54..b2eaf41 100644
--- a/tools/gonk_tools/plot.py
+++ b/tools/gonk_tools/plot.py
@@ -199,7 +199,7 @@
                 power_values[i].append(power[i])
 
     # Plot vbus and vshunt values.
-    _fig, (ax1, ax2, ax3) = plt.subplots(
+    _fig, (ax1, ax2, ax3) = plt.subplots(  # type: ignore
         3, 1, layout='constrained', figsize=[11.67, 8.27]
     )