Fix multi-panel visual test: add title="" to avoid layout shift

The multi-panel frameon=False test produced different title positions
across Python versions due to bbox_inches="tight" cropping differently
when axes frames are off. Adding title="" eliminates the layout-sensitive
text — the behavioral multi-panel assertion already covers title handling.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: timtreis

tests/_images/Show_frameon_false_multi_panel.png

@@ -33,11 +33,10 @@ def test_plot_frameon_false_single_panel(self, sdata_blobs: SpatialData):
         """Visual test: frameon=False hides axes decorations on a single panel (regression for #204)."""
         sdata_blobs.pl.render_images(element="blobs_image").pl.show(frameon=False)
 
-    def test_visual_frameon_false_multi_panel(self, sdata_blobs: SpatialData):
+    def test_plot_frameon_false_multi_panel(self, sdata_blobs: SpatialData):
         """Visual test: frameon=False hides axes decorations on all panels (regression for #204)."""
         set_transformation(sdata_blobs["blobs_image"], Identity(), "second_cs")
-        sdata_blobs.pl.render_images(element="blobs_image").pl.show(frameon=False)
-        self.compare("Show_frameon_false_multi_panel", tolerance=20)
+        sdata_blobs.pl.render_images(element="blobs_image").pl.show(frameon=False, title="")
 
     def test_plot_no_decorations(self, sdata_blobs: SpatialData):
         """Visual test: frameon=False + title='' produces just the plot content (regression for #204)."""