Update shinytest2 snapshots for panel.border fix

The element_blank panel.border fix intentionally removes empty shapes
from the plotly output. Update the shinytest2 JSON snapshots to reflect
this improvement.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: cpsievert

inst/examples/shiny/event_data/tests/testthat/_snaps/shinytest2/001.json

@@ -328,24 +328,7 @@
             "hoverformat": ".2f"
           },
           "shapes": [
-            {
-              "type": "rect",
-              "fillcolor": null,
-              "line": {
-                "color": null,
-                "width": 0,
-                "linetype": [
 
-                ]
-              },
-              "yref": "paper",
-              "xref": "paper",
-              "layer": "below",
-              "x0": 0,
-              "x1": 1,
-              "y0": 0,
-              "y1": 1
-            }
           ],
           "showlegend": false,
           "legend": {

inst/examples/shiny/event_data/tests/testthat/_snaps/shinytest2/002.json

@@ -331,24 +331,7 @@
             "hoverformat": ".2f"
           },
           "shapes": [
-            {
-              "type": "rect",
-              "fillcolor": null,
-              "line": {
-                "color": null,
-                "width": 0,
-                "linetype": [
 
-                ]
-              },
-              "yref": "paper",
-              "xref": "paper",
-              "layer": "below",
-              "x0": 0,
-              "x1": 1,
-              "y0": 0,
-              "y1": 1
-            }
           ],
           "showlegend": false,
           "legend": {

inst/examples/shiny/event_data/tests/testthat/_snaps/shinytest2/003.json

@@ -335,24 +335,7 @@
             "hoverformat": ".2f"
           },
           "shapes": [
-            {
-              "type": "rect",
-              "fillcolor": null,
-              "line": {
-                "color": null,
-                "width": 0,
-                "linetype": [
 
-                ]
-              },
-              "yref": "paper",
-              "xref": "paper",
-              "layer": "below",
-              "x0": 0,
-              "x1": 1,
-              "y0": 0,
-              "y1": 1
-            }
           ],
           "showlegend": false,
           "legend": {

inst/examples/shiny/event_data/tests/testthat/_snaps/shinytest2/004.json

@@ -336,24 +336,7 @@
             "hoverformat": ".2f"
           },
           "shapes": [
-            {
-              "type": "rect",
-              "fillcolor": null,
-              "line": {
-                "color": null,
-                "width": 0,
-                "linetype": [
 
-                ]
-              },
-              "yref": "paper",
-              "xref": "paper",
-              "layer": "below",
-              "x0": 0,
-              "x1": 1,
-              "y0": 0,
-              "y1": 1
-            }
           ],
           "showlegend": false,
           "legend": {