Update histogram.py

Remove unnecessary keyword argument that was commented out.

Author: AdvancedImagingUTSW

src/navigate/controller/sub_controllers/histogram.py

@@ -276,7 +276,6 @@ def _clear_histogram(self) -> None:
                 "style": "italic",
                 "color": "gray",
             },
-            # fontstyle="italic",
             ha="center",
             va="center",
             bbox=dict(facecolor="white", edgecolor="none", boxstyle="round,pad=0.5"),